A great, curated collection of electronic music. You can search by music type (like dubstep, house, hip hop) and also by license (attribution, share alike, etc.). There are ads on this site, and some of them look like download buttons, so be careful. This site also has a good database of sound effects. Even a dedicated section for video games.
“SampleSwap first started in 2001 as a folder of audio samples hosted on a hotline server running on a computer in Canton’s basement. In 2003, the collection was uploaded to the WWW for the first time. The entire collection has always been made available for free.
Over the past 16 years, members have uploaded their own creations and rare finds for consideration in the collection. Canton listens to every upload, and decides which ones should be folded into the master collection.
Every sample is trimmed, normalized, renamed, and organized by hand.”