I purchased an AirPrint enabled printer last year and have been very happy with it. But, Shawn Blanc offers some options for those without AirPrint enabled printers that would like to print from their iOS devices.
Shawn ended up settling on Printopia:
Though I mostly use Printopia for actually printing out documents, it’s helpful to have its additional features.
Those features include running in the background with no Menu Bar or Dock icon, printing to any folder on your Mac, and being able to “print” directly to various applications.