We just took delivery of a new iPod touch. Without hesitation, the first thing we tried to do (after oohing and aahing a bit at the WiFi iTunes Store) was hack the device to put third-party applications on it in the same manner as the iPhone. Unfortunately, the current iPhone methodology doesn't work for the iPod touch, and here's why:
The super-simple AppTapp method, which allows you to simply run one application from your desktop computer that jailbreaks the iPhone and puts Installer.app on the device through which other applications can be installed directly doesn't work because it hasn't yet been updated to use the iPod touch's firmware/software revision, which is labeled 1.1.
After doing a restore on the device through iTunes under Mac OS X, the new firmware file is downloaded to ~/iTunes/iPod Software updates and labeled iPod1,1_1.1_3A101a_Restore.ipsw. However, there's no way to select an individual firmware file from disk with AppTapp.
Even if there were, there's another problem that obviates use of our manual 5-step hacking method (created just before AppTapp was released): it looks like Apple has changed the encryption scheme for the iPod touch firmware file, meaning that a new method will need to be discovered for cracking this file, getting the appropriate software out and jailbreaking the iPod touch. We'll hold our breath, however, as such a method should sprout shortly from the ingenious iPhone hacking community.