Soundsnap.com Comments: Thousands of free sound effects and loops, with tagged browsing. Limitations: Free for commercial and non-commercial use, but must comply with their terms of use (attribution optional, but no reselling unless part of a complete work). See the copyright/legal section at the bottom of the FAQ for more information.

FlashZen Comments: Great collection of music loops meant specifically for use in Flash audio. Limitations: Check the site's Creative Commons license for attribution requirements.

FlashKit Comments: Among other things, FlashKit offers a large collection of audio loops and effects for use in Flash movies. Limitations: Read the usage guidelines for the different usage rights for various tracks.

Incompetech Comments: Browse by feel or genre. Music only. Limitations: Music must be credited in your work. Author (Kevin Macloed) requests a $5 donation to support the site, but not required.

Common Content Comments: Searchable catalog of work licensed under Creative Commons; includes images and movies as well. Limitations: Check details on each audio download for licensing and attribution requirements under Creative Commons.

RoyaltyFreeMusic.com Comments: Music, loops, beats, sound effects, even ringtones. Limitations: Only the sound clips on the page provided are free. Everything else on the site is paid.

CCMixter Comments: A site containing remixes licensed under Creative Commons. It can be a little confusing to figure out how to download in MP3 format, but you'll get there. Limitations: Check the Creative Commons license associated with each track before you use it. According to the FAQ, most of the music on the site is free and legal for any use, anywhere, but you're advised to check individual tracks for different licensing and restrictions.

Free-Loops.com Comments: A wide variety of downloadable loops and audio clips. Limitations: Site says “free for personal use only” at the very bottom. May be restrictions for commercial use.

SoundSource Comments: Sounds, effects, and music samples. Check the upper right hand corner to switch the language to English if you get lost. Limitations: Check Creative Commons licensing for attribution requirements; some rights reserved.

NewGrounds Audio Comments: Anything from midi loops to wav remixes to voice audio clips – some good, some downright awful. Limitations: Check each track for licensing and attribution requirements. Be aware that users on Newgrounds may create remixes/loops without permission of the original copyright holder.

Rekkerd.org Loops Comments: Collections of royalty-free music loops. Limitations: None; donation requested but not required.

FreeSound Comments: Royalty-free sounds under Creative Commons. Limitations: Check Creative Commons licensing for attribution requirements.

Ljudo Comments: Over 1200 searchable, royalty-free sound effects in MP3 and RealPlayer format (people still use RealPlayer?) If you keep clicking your language and wondering why you're not getting anywhere, look for the little button at the bottom that says “Got the right language? Click here!” Limitations: Check Creative Commons licensing for attribution requirements.

Freeze.com Comments: Downloadable packet of free sound effects. Limitations: May require e-mail registration before use.