There is a very manual tutorial up at xpwn.co.uk on how to Jailbreak your iPhone with the 2.1 firmware:

T14:19 <+geeb> http://xpwn.co.uk/2.1JBtut.txt
14:19 <+geeb> 2.1 3g jailbreak tutorial
14:22 < comm> geeb: has it been tested?
14:22 <+geeb> comm
14:22 <+geeb> yes by me
14:22 <+geeb> and others in #xpwn are running it now

The following are the instructions

Download the 2.1 firmware <--http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone/061-5198.20080909.K3294/iPhone1,2_2.1_5F136_Restore.ipsw

I was recently having issues with my phone not being able to use 3G, and I thought it might have been a firmware or possibly hardware issue. But after troubleshooting for some time, I found that it was in fact applications crashing or firmware bugs. Hearing more and more reports of network issues with 3G and iPhones, Wired Magazine decided to do a survey of 3G coverage across america.

Touted as the first 3G enabled phone for T-Mobiles network.

Samsung's 3G SGH-T639 being sold by T-Mobile - This summer, we all got our hopes up when Samsung's (apparently 3G-enabled) SGH-T639 found its way into the FCC, and now that the handset is reportedly on sale in New York City, it'd be a great time to work yourself into a tizzy once more.