The iPod Touch 2G jailbreak was first shown in January. It had to be applied every time the iPod was booted. The iphone-dev team just released the 24kpwn LLB patch to allow for a persistent jailbreak. The team had been hanging on to this patch because there was the possibility the exploit could be used on future iPhone versions. Unfortunately, a group started selling the code, so the team was forced to release it for free. iPod owners are certainly happy though. There is a tutorial available for updating a factory reset iPod (backup link). The team will include the patch in future official tools.
UPDATE: [cptfalcon] pointed out a post that covers the technical details of the exploit.