4.3.2 is out...I wouldn't suggest jailbreaking an iPod touch... I've tried it before. Its awesome and cool looking but it reduces your battery by so much. Plus any games that don't have online saves...you'll have to start over again.
If you have 4.2.1, do not upgrade. You can use greenpois0n to jailbreak it. I'm not sure about 4.3, 4.3.1, or 4.3.2 though.
Sent from my iPod touch using WiiHacks