HUGE list of icons (and some wallpaper) that are geek-centric. They’re in ICO format (I’m guessing a Windows desktop (or whatever they call it) thing) and I have yet to play with any of them, so I’m not sure how easy they are to convert to other platforms. Still, impresssive.
Nice. Everything a growing geek needs!
.ICO is an icon format for windows, don’t know if it works on OSX.
Not directly, but there seems to be a bunch of conversion utilities. Here’s an online one that appears to work in both directions.