Click here to learn how to use any .wav file as sounds on your computer!
(eg. 'You've Got Mail' or 'Exit Windows.' ) Instructions for Windows. - Sounds
These guys have got over 400 sound clips! You should really go see what they have.

Cheyenne Mountain Stargate Sounds
Some zipped files with great this site is a host for some clips I personally made!  (The season six stuff) - Multimedia: Sound Clips
Lots of fun clips here, Seperated by character. - Season One: Season One Sounds
Sound clips from season one by episode.

Dedicated To Stargate SG-1 - Sound Bytes
Lots of great sound clips here, organized by character.
Go to 'Sound Bytes' in the menu.

Moon-Catchin.Net - Stargate Sounds By Episode
Good clips here; nice and loud, not the kind you can barely hear. :-)