Devices Supported: iPhone 2G, iPhone 3G, iPhone 3G[S] iPod touch 1st Gen, iPod touch 2nd Gen (No support for iPod touch 3rd Gen yet)
Computer OS Supported: Mac
Firmware Supported: 3.1
Necessary Downloads: Pwnage Tool 3.1.3 and 3.1 IPSW file for your device.
Pwnage Tool 3.1.3:
Go to here, click on the second drop down bar and find your device with the 3.1 firmware and download it.
(These are the direct downloads of ipsw files from Apple's servers, we have not uploaded them).
Then just use the step-by-step instructions provided for you in the program.
For more information on your specific device be sure to visit the Dev Team blog.