I've been a big fan of Printopia since it first came out. It allows you to print from an iOS device to any printer on a wireless network or directly connected to a Mac.
After Apple's half-hearted AirPrint feature was launched, people were pretty upset to learn that it worked on only a handful of HP printers. Printopia fixed that with an app that sits in your system preference window, and gets you printing to just about any printer you have. The app requires a Wi-Fi network for connectivity.
The new version adds password security, unlimited virtual printers, and some new customization options giving users full access to printer settings, like page size, paper tray and color settings. It retains the print to Mac function which sends a JPEG or PDF to your Mac, and also allows you to send JPEG and PDFs to Dropbox or Evernote. I've used the original version since it came out and it has been flawless. Current owners can get the update for free by clicking on Printopia in System Preferences, new users will pay US$19.95 and anyone can try a 7 day free trial.