Worried about jailbreaking your iPhone now that iPhone OS 3.0.1 is out, don’t be because according to the iphone blog you can safely update to iPhone OS 3.0.1 and still jailbreak the iPhone.
Apparently redsn0w v0.8 can be reused to jailbreak after allowing iTunes to update to iPhone OS 3.0.1. The trick is that when redsn0w asks you to identify the ISPW used, just point it at the 3.0 IPSW rather than the 3.0.1 IPSW.
Once done then reinstall ultrasn0w 0.9 if you need to unlock your iPhone. Unfortunately iPhone OS 3.0.1 kills off the use of purplesn0w.