FreeSFX offers more than 3000 free sound effects and music tracks. All downloads are mp3:s and to get access you have to become a member.
Freesound.org has been around since 2006 and over the years they have collected over 100,000 sound effects and music tracks. The uploader gets to choose between different licenses so make sure you select files that properly suits your project.
Hiss and a Roar
Tim Prebble does not only sell sound effect libraries, he also offers parts of them for free. The only thing he asks in return is that you subscribe to his newsletter.
Mysoundfx.com has free sound effects, ringtones and background music. The sounds are licensed Creative Commons 3.0 Unported which means you can share, remix and use them commercially as long as you credit MySoundFX.
The free sound effects at PacDV seems to be very similar to those at SoundJay. You can download them directly without registering. The sound effects are either mp3 or wav.
Sound Designer Samuel Justice has worked on projects like Amnesia: A Machine for Pigs and Dear Esther. Samuel is also kind enough to share some of his recordings on his blog (almost) every week.
Partners in Rhyme
The Partners In Rhyme site has been around since 1996. Their main focus is to sell royalty free music and sound effects but they also have a free section. The site is somewhat chaotic and quite tricky to navigate.
SFXSource is in essence an audio stock site. They do however offer some useful free sound effects.
Stephan Schutze has a passion for sounds. He’s collected over 20,000 sound effects which he shares with the world for free. There are restrictions though since the collection is covered by a Creative Commons NonCommercial license.
The audio at Sound Jay seems to be similar to those at PacDV. Every free sound effect is available in both wav and mp3. No registration necessary.
SoundFX Now has about 1,000 free sound effects. Download individual mp3:s or make a small donation to get the full high-quality wav collection.
Frank Bry’s site The Recordist has a collection of free quality sounds in mp3 format. Note that the sound effects are only free for personal use. If you want to use them in a project you’ll have to buy a license.