iOS 4.3.4 hitting the streets, and already posters at Redmond Pie claim to have a PwnageTool 4.3.3 bundle that unlocks it. Ready to roll on every device except for the iPad 2, this tethered jailbreak brings back Cydia and anything else you might have missed after foolishly updating this afternoon. Any brave souls ready to jump in (at their own risk of course) immediately can find directions at the source link below, let us know how it's worked for you in the comments.
Update: The iPhone Dev-Team has updated its redsn0w tool, also based on existing exploits, for all your tethered jailbreaking needs. Of course, they still recommend you stick with iOS 4.3.3 for untethered convenience, so stay far away from the update button or modify your version number if nefarious PDFs are a friend and not an enemy to you. [Thanks to everyone who sent this in]