The 3.0.1 release is a “branch” from 3.0 that occurs (code-wise) before all the 3.1 betas. The programs redsn0w needs to change for the jailbreak are identical when you compare the 3.0 and 3.0.1 versions. It seems pretty much the only changes Apple made were for the SMS bug, which affects programs that redsn0w doesn’t touch. That’s why you can re-use redsn0w 0.8 on 3.0.1 even though it was written for 3.0.
As I explained yesterday, you can still jailbreak your iPhone running 3.0.1 running RedSn0w and pointing it to firmware 3.0. Then, should you want to unlock, simply install UltraSn0w from Cydia if your are on an iphone 3G or 3GS. If you’re on a 2G, just use RedSn0w to jailbreak and unlock.
The Dev Team says that they will update RedSn0w at some point so it recognizes firmware 3.0.1 but it will just be “aesthetic” changes, so there is no reason to wait for it.
For more detailed information about jailbreaking and unlocking, I recommend you check out the jailbreak page and the unlock page of this site. It is updated with the latest info.