If you can get it to load, Jailbreak Me is the one of the simplest jailbreak solutions yet. Just visit the site on Mobile Safari and — if you can get it to load — your iOS device running 4.0 or 4.0.1 is jailbroken, no reboot required.
Unfortunately, when it was released yesterday, there were caveats: FaceTime and MMS got knocked out of commission with the jailbreak.
Luckily, Jailbreakme.com has now been updated with a fix to the FaceTime and MMS issues. Already jailbroken? Just open Cydia and upgrade when you’re prompted to.
Finally, here’s the best news: if you’re waiting for a compatible unlock, it should be available in the next 48 hours.