The sites listed below offer royalty-free music that ranges from totally free to pay per use.  Please make sure to pay special attention to the stipulations of any Creative Commons-licensed music, as certain CC licenses require attribution to the original author or prohibit commercial use of the material.
(also checkout Garageband for Mac)

Sorry for not having each site hyperlinked but I didn’t have the time to do that. Maybe I can go back and copy the html from my joomla site and it will automatically link them together.

http://mobygratis.com :: this portion of moby.com, ‘film music’, is for independent and non-profit filmmakers, film students, and anyone in need of free music for their independent, non-profit film, video, or short.
http://Incompetech.com :: All music on this page is provided royalty-free. This work is licensed under a Creative Commons License.
http://incompetech.com/m/c/royalty-free/
http://jamendo.com :: On Jamendo artists allow anyone to download and share their music. It’s free, legal and unlimited.
http://openmusicarchive.org :: Open Music Archive is a collaborative project, initiated by artists Eileen Simpson & Ben White, to source, digitise and distribute out-of-copyright sound recordings. The archive is open for anyone to use and contribute to.
http://opsound.org :: Opsound is a gift economy in action, an experiment in applying the model of free software to music. Musicians and sound artists are invited to add their work to the Opsound pool using a copyleft license developed by Creative Commons. Listeners are invited to download, share, remix, and reimagine.
http://ccmixter.org :: ccMixter is a community remix site sponsored by Creative Commons
http://freesound.org :: The Freesound Project, collaborative database of creative-commons licensed sound for musicians and sound lovers. Have you freed your sound today?
http://classiccat.net :: free classical music

The following sites offer music that can be used royalty-free after a certain base fee is paid:

http://partnersinrhyme.com :: Royalty free music to download for Film, TV, Video and Websites, plus free sound effects, free music loops, free midi files and free audio software.
http://stockmusic.net :: Pay Once. Use Forever
http://royaltyfreemusic.com :: Royalty free music and stock music for production, multimedia projects, film, television, video, advertising, and on hold music applications.
http://shockwave-sound.com :: Royalty free background music, buyout music loops. Listen online, purchase on secure server, use as much as you like. Delivered by instant download
http://smartsound.com :: The world’s largest and most customizable music library
http://opuzz.com :: Royalty free music background music. Royalty free background music downloads & CDs for any usage. All buyout royalty free background music, pay once
http://digitaljuice.com (but it’s a bit spendy) :: Digital Juice is the world leader in royalty-free professional animations, stock footage, music, layered graphics, clip art, and templates.
http://stock20.com :: Broadcast Quality Royal Free Production Music *$20 Song
ebay.com :: Royalty Free music
http://instantbackgroundmusic.com :: Instantly Download Royalty Free Professional Instrumental Background Music Productions for Camtasia Video Presentations, YouTube video projects
http://musicbakery.com :: Royalty free music downloads and CD s. Download premium quality royalty free music for websites, podcasts, video & film. Features a buyout production music
http://neosounds.com :: Royalty Free Music Tracks and Loops for Video, Radio, TV and film production, Games, Flash, Presentations. Instant Downloads.
http://freeplaymusic.com :: Freeplay Music, Highest Quality Broadcast Production Music Library, Free Mp3 Music Download, See Terms Of Use, Country,Hip Hop,Rap,Techno,Song with Lyrics
http://beatsuite.com :: royalty free music library featuring thousands of production tracks, flash loops and sound effects. Preview, Purchase, Download.
http://uniquetracks.com :: Royalty Free Music provider UnqiueTracks is something different. Download from our music library and give us a listen, we have classical, sound effects
http://soundzabound.com (for schools) :: Soundzabound is the ONLY royalty free music library which meets all the licensing and technology requirements needed for education!
http://premiumbeat.com :: Royalty Free Music, professional tracks and Flash loops for website, background music, film, radio and television. Preview and download instantly.
http://productiontrax.com :: Royalty free music and sound effects library, stock footage, and stock photos. Create buyout soundtracks or download videos and photos, stock music
http://sounddogs.com :: 400000 Sound Effects and Production Music Tracks. Download WAV AIF, and Mp3 Sound Effects, Production Music, Surround Sound Effects, Sound Effects CDs
http://bbm.net :: Royalty free music from bbm.net. Thousands of royalty free music selections from professionals all over the world.
http://flyinghands.com :: Stock music and royalty free music downloads. MP3 tracks: Search, preview and buy online. Audio CDs: More tracks, better music . Instrumental royalty free
http://iamusic.com :: Royalty free music you can download online in mp3 format. Finally, that Hollywood soundtrack sound in a royalty free music library.
http://ibaudio.com :: 100% Royalty Free Music, Stock Music – A high quality music library for producers and multimedia developers. NO license hassles or cue sheets to file
http://studioloopstudio.com :: The first and finest collection of original sound effects and royalty-free music optimized for interactive media. Custom sound design and music also
http://vpdinfo.com/download.htm :: A reference site to help identify public domain songs and public domain music . . . lists of public domain music, royalty free music recordings
http://buyoutmusictracks.com :: Royalty Free Music by Alan Steward, CDs starting at $29.95, Instant Downloads, Affordable Production Library for Video, Broadcast and Multi Media
http://royaltyfree.com :: Royalty free music and buyout music for production, multimedia projects, film, television, video, advertising, music on hold, and background music
http://whitebeetle.com :: Browse our royalty free music by category or by using our Quick Search facility, make your choice and decide which format you require
http://crankcity.com :: free cd library at CrankCity. Buy Royalty Free CD collections today.
http://sound-ideas :: Sound Ideas is the world’s largest publisher of professional sound effects, royalty free production music and production elements.
http://allmusiclibrary.com :: Royalty-Free Music from All Music Library
http://studiocutz.com :: The Studio Cutz Production Music Library is a collection of the highest quality royalty free music (or buyout music) available for use in a multitude of production areas. Royalty free sound effects are available for downloads.
http://instantdownloadmusic.com :: The place to instantly purchase professional background theme music with a ‘Royalty-Free’ license delivered in high quality Mp3 format.
http://loopsound.com :: License Royalty free music Full tracks, Loops and Cuts from our stock music library. Download production music for TV, podcasts and Flash web sites.
http://gettyimages.com/Music :: Original music. Independent artists. Simple licensing.
http://audiosparx.com :: Celebrating 12 Years of Providing Quality Content to the Global Audio Community! Sounds are Free to Preview – Purchase to Download in WAV, MP3, AIFF, AU, or WMA Format
http://cssmusic.com :: Superb quality of royalty free buyout production music and sound effects available now. Over 300 volumes and 10000 tracks may be purchased on CD, CD-ROM
http://soundrangers.com :: The first and finest collection of original sound effects and royalty-free music optimized for interactive media. Custom sound design and music also
http://audiojungle.net :: AudioJungle is a brand new audio community serving up thousands of stock music loops and audio effects by independent authors for use in your projects.
http://musicloops.com :: Royalty Free Music Loops, Full Length Tracks and Edits, Immediate Download, Lifetime License, no ASCAP or BMI.
http://music2hues.com :: Music 2 Hues is a worldwide supplier of royalty-free production music and sound effects. With over 100 audio CD’s, and over 1000 buyout music tracks for download, we’re confident you’ll find a music track to fit your next production.
http://smartassmusic.com :: Royalty Free Music, Digital Audio, Composition, Custom Audio, Music Production and Session Musicians
http://stockmusicstore.com :: Your best source for modern high quality music
http://ntracks.com :: Your best choice for buyout music, production music and commercial background music. All clips are downloadable and royalty free.
http://massivetracks.net/royalty-free-music.htm :: Royalty Free Music, Loops, Voiceover for Immediate Download for TV, Video, Multimedia, CD, Games, Backgroundmusic, Internet, Musiclibrary
http://chrisworthproductions.com :: Royalty free music, stock music, buyout music for soundtracks, productions, video, television, websites, computer games, music on hold, and background music applications. Listen to and download music samples from our online catalogue.
http://expertaudioshop.com :: An audio professionals resource for royalty-free sound effects, production elements, sound effect downloads and sound library products. At Expert Sound Shop our product offerings include sound effects from Sound Ideas, BBC, Digiffects, Serafine and many more publishers.
http://nvmdigital.com :: NVM Digital – Library of royalty-free (copyright-free) music, photo library, books, maps, special interest CD-ROMs, Arts and Crafts from the Lakes and Dales
http://allmusiclibrary.com :: Download any royalty-free music track instantly for just $25 or less
http://search.stephenarnoldmusic.com :: We’re Artists – not Agents. All substance, no fluff. All needles, no haystack. Just real, high-quality tracks written, arranged and engineered by us. That means you’ll find what you’re looking for fast. Very fast. Save time, save sanity and save face by bringing the good music. So get in. Get the good stuff. And get out.
http://sonomic.com :: Download over 250,000 sound effects, samples and royalty free music tracks from the biggest and best libraries, including Sound Ideas, Zero-G, BBC and more.
http://studio1downloads.com :: Royalty Free Music for Downloads. Video Backgrounds, Web Templates, Graphics and Stock Photos all available as downloads. Demos online.
http://royaltyfreemusicmp3.com :: Download High quality Royalty free music, free Background Music, stock music, for video, film, TV, radio, multimedia, internet.
http://davenportmusic.com :: Royalty free music for production and music on hold – 3 CDs for $99. Buyout music CDs and instant mp3 downloads at $19.95 each. K-12 educational packages
http://notepadmusic.com :: Notepad Music – composing custom music, songs, advertising music, jingles, stock music, library music, television themes, television music.