I’ve finally found some samples and I didn’t had to search really far: I took sounds from World of Goo.
So go test the latest version of SoundEvents. You need a browser compatible with HTML5′s audio tag, preferably Firefox. Chrome introduces a delay before playing the sound even though it is cached when you open the page. And I haven’t tested Safari.
The only problem is that I cannot redistribute those sounds since they are not liberally licensed. I tried to use the sounds of Wormux as an alternative but for some reason the sound is not playing in my application even though they do play when I drag & drop them in the browser. It’s too late now, I’ll search for alternatives tomorrow.
Do you know any Open game with interesting samples?