For iPhone and iPod touch owners who want the benefit of the recently released 3.0 firmware, but also want to run jailbroken applications, the iPhone Dev Team has just released an updated PwnageTool for Mac OS X systems. There are quite a few caveats and qualifications at this stage, such as the fact that it won't work with second-gen iPod touch devices or the new 3G S phones, but updated tools should arrive shortly.
Furthermore, if you have previously unlocked your phone for use with a carrier other than AT&T (or the authorized carrier in your country), you are advised not to use this version of Pwnage as it will jailbreak your phone but also relock it back to the original carrier assignment. Those looking to unlock their 3.0 phones will have to wait until Ultrasnow is available for this – which should be anytime now. Full instructions, along with download links and a few other things to consider, are available at the iPhone Dev Team blog