iPhone dev team’s pwnage tool v3.1.4 is out supporting firmware 3.1.2. The dev team’s official post gives details. This lets you unlockers that need to update without updating your baseband do so. Pwnage currently only supports OSX so if you don’t have a MAC you are left with blackra1n as your only option at this time.

The pwnage guide posted on this site still applies to this release other than the updated download links at the bottom of the post.

Also, after you are done jailbreaking, make sure you select the option in the Cydia home page to save your ECID SHSH signature so you can always restore to 3.1.2 firmware in the future no matter what Apple decides you should do. This applies to both pwnage and blackra1n users.