I recently came across this awesome tool called as3sfxr on the freegamer blog.
Game SFX maker in FlashThis is really cool. The software (Flash) is embedded in the blog post and you can try it out right there. Just try fiddling around with the different buttons and see what it generates. I don't know if its appropriate to create sounds for us as they are more retro/sci-fi style, but its possible we could make use of it. Its fun to play around with though. Try clicking randomize and then hit mutate a couple dozen times and notice how the sound gets tweaked.
The generator code is open source too.
The project page is here.