While there is a jailbreak currently available for iOS 4.3 using sn0wbreeze it is tethered and many jailbreak apps don’t support it so for the majority of users it’s going to be better to wait for an iOS 4.3.1 jailbreak. 4.3.1 firmware is expected in the next couple of weeks so it’s widely expected that the fully baked jailbreaks are going to be held off until it’s released.
Recently BGR got a hands on of iOS 4.3.1 firmware running on an iPhone 4 and reported that it seems to be largely just bug fixes along with a slight increase in battery life.
As far as the jailbreak itself goes there are several people working on it so it should be available relatively shortly after 4.3.1 is released and should be available for the iPhone 3GS, iPhone 4, iPod touch 3G, iPod touch 4G, iPad and iPad 2. iOS 4.3.1 is expected to be released in the next one to two weeks.
Update: iOS 4.3.1 has now been released, click here for the full details.