Spirit jailbreaks iPhone, iPod Touch and iPad with OS 3.x. It’s a userland jailbreak and has been one of the easiest to use to date. When iTunes 9.2 was released, devices jailbroken with Spirit still worked with it, but you couldn’t jailbreak devices after it was installed.
A fix has been released for this issue now which makes Spirit compatible with iTunes 9.2. The fix can be downloaded from here, although it’s Windows only.