Yes, there is a jailbreak for the iPod Touch 4G.
If you are running iOS 4.1, the two best jailbreak methods to use are greenpois0n and limera1n (both are untethered). If you are on iOS 4.2.1, use greenpois0n for an untethered jailbreak (redsn0w does jailbreak iOS 4.2.1, but it is tethered). If you are on iOS 4.3.1, use redsn0w 0.9.6 RC12 to obtain an untethered jailbreak.
I hope this helps!
