redsn0w is an easy to use, multi-platform, multi-device jailbreaking and unlocking (iPhone 2G only) tool for the iPhone 2G (original iPhone), the iPhone 3G (but not the 3GS) and also the iPod touch (first and second generation). Currently it is available for Windows and Mac OS X (there are some issues using redsn0w with OS X PPC, please use an Intel Mac until we have this problem resolved).
I just want to jailbreak, not unlock. I'll be able to just do that, right?
Crap, I am on PPC
Yes, just use redsn0w. Great tutorials on Iclarified.com
Yes, Redsnow will do that.