With the iOS 5.1.1 Untethered Jailbreak being released recently in the form of Absinthe 2.0 there are nearly one million new Jailbroken iOS devices. I am sure one of the reasons why so many people Jailbroke their iPhone, iPod Touch or iPad was to get Siri functioning. Unfortunately the most popular methods of installing Siri on Jailbroken iOS devices, Spire is not compatible with the iOS 5.1.1 firmware.
iFouineil 