TruPrint is a premium jailbreak iOS app from the makers of MyWi that brings iPhone AirPrint compatibility to most printers. As you may know, very few printers support Apple's AirPrint which allows you to print directly from your iPhone; TruPrint opens up AirPrint to a plethora of different printers. However, if you really need to print from your iOS device and AirPrint is a no go for you, you probably won't mind shelling out the cash.
The app costs $9.99, and is also available with a three-day trial so you can try it with your printers.
Once installed, TruPrint automatically discovers printers, and requires no setup whatsoever. It works on all iDevices running iOS 4.2 or newer.
You can get TruPrint by searching Cydia for it. If you've decided that this alone is worth jailbreaking your iDevice, head over to this page for a quick rundown of which tool to use, depending on what version of iOS you're currently on.
Here's a TruPrint demo: