I’ve Been Thunderstruck

I’ve used Soundsnap a number of times in my projects, and I absolutely love it. With categories like Animals, Comic and Film FX, Nature and Science Fiction, chances are there is a sound effect or music loop that fits your exact project. The best thing about this site is that all files are free, are in the public domain, and you do not have to give credit to the authors (though it’s certainly a nice thing to do). Attribution is optional, and you can even use them for commercial work (aside from selling a CD with them on it). If you use sound in your projects, you should absolutely check this out.