Pwnagetool for mac was released before redsn0w jailbreak and ultrasn0w unlock came into the unlocking and jailbreaking market. It was a 3.0 version and was useful to jailbreak Original iPhone (1st Generation), Original iPod touch (1st Generation) and the iPhone 3G.
Now the team has released a newer version, though it has not talked about it publicly, we have noticed the release in the torrent site TPB. The update has come with fix to some of the previous issues and updates to the Icy app. But still the issue is that Pwnagetool is available only for mac users, and Windows users have to keep waiting for the release for their OS.
Apart from these tools, there is QuickPWN 3.0 which can also help in jailbreaking the iPhone 3.0 OS.
Here is the info given in the TPB site –
PwnageTool 3.01 is a Mac based iPhone firmware creation tool for creating custom ipsw/firmware for the 1st gen iPod Touch, iPhone and iPhone 3G (NOT 3GS). This version supports the 3.0 firmware from Apple. For full details (which are often updated) visit the iphone DevTeam blog. http://blog.iphone-dev.org
This version fixes compatibility with the PPC version of Mac OS X also the Icy package is updated. This DOES NOT work with version 3.1 of the iPhone OS.
Btw i had posted a tutorial on how to unlock iPhone 3G 3.0 firmware, but using redsn0w and ultrasn0w. Also the iPhone 3GS people can be happy with the purplera1n jailbreak tool release, not by the iPhone Dev team though. That can be used to jailbreak and then ultrasn0w works to unlock the iPhone 3GS.