-Any iPad, iPhone, or iPod touch on firmware 3.1.2, 3.1.3, or 3.2.
-An activated device: one not stuck on the Connect to iTunes or Emergency Call screen.
-Any version of iTunes 9 (including 9.1.1).
-Syncing with iTunes before trying this highly recommended.
Note: On iPad, all this is still sort of beta. Some packages in Cydia, not designed for iPad, might screw up your system and require you to restore. Be careful. (And no, Cydia's appearance is not final.)
For Windows click here
For MAC click here
Further information is provided on the Spirit site here
Props to @comex for his hard work, we all appreciate it!!!