This is a quick tut on jailbreaking iPhone, 3g, and ipod touch 1g 2g (not 3g)
with redsn0w 0.7.2.

ok, first you have to upgrade to 3.1. buy it, or download an ipsw, it doesnt

next, open redsn0w 0.7.2+ and connect your device, select a 3.0 ipsw. then click next. follow the on screen instructions to put your iDevice in dfu mode.
click next again, and it will tell you its uploading the ramdisk and a load of other random crap. now just wait for the process to finish. congrats your jb'd on 3.1(.1)

hope this helps
~Pwn THT Phwn~