One look at the nine categories they offer and you know you're in for hours of listening pleasure...
...by that I mean quickly scanning a few short samples and realizing that there's way too much stuff in here to understand right away (and they don't give you any download links).
Fortunately there's a solution.
First check out some sounds then I'll give you an easy way to make use of them.
The next little piece of the puzzle comes from Audio Hijack. This is freeware that lets you record your system audio, from a specific application or the whole system.
Audio Hijack is what you use when you need to record a sound from your browser. I found it the day I wanted to record pings and chimes from Skype for a DJ set.
I think it has a ten-minute timeout that's designed to make you upgrade to Pro version, but for recording short things it works great. Get some dolphin sounds off youtube or whatever.
Part 3: when you want to tweak and mangle your new field recordings, "Bleeps and Sweeps Rack" is waiting for you -- drop some vocal samples from the British Library in there and garble them up.