The iPhone Dev Team released Pwnage 2.0 earlier today.
Confused? iClarified has posted a detailed tutorial on how to use it. Do note that iPhone 3G have not been unlocked.
Download is available here and here.
Update: Pwnage has been updated to 2.0.1! Do note that if PwnageTool 2.0 pwned your phone correctly the first time, you [...]

What is Customize 2.0?

Customize 2.0 is a whole new way to take control of your iPhone. Building on the popularity of the original, Customize 2.0 makes it even easier to modify your phone just the way you like it.
This new version is not only a native iPhone application but also a web-based theme management system, [...]