Apple today released iOS 4.3.5 which similar to iOS 4.3.4 will block the recent JailbreakMe tool released by comex. Do not update if you want to remain jailbroken.
If you have a device other than the iPad 2 and have not already saved your iOS 4.3.3 SHSH Blobs you can use iFaith to save them. You can find instructions on how to do that here.
If you want to jailbreak but haven't yet, you can find instructions on how to jailbreak here.
