Apple's latest mobile-operating-system update introduces a much-demanded feature: wireless printing. Problem is, it will only officially print from printers labeled "AirPrint-compatible," which you likely don't own. However, if you want to print from just about any printer, there's a mod for that. AirPrint Activator offers a solution for Macs to set up wireless printing with iOS 4.2 with any printer shared on your network.

 Here's how to set it up, with instructions courtesy of the hack's maker, Netputing. You will need the following:
Mac OS X Snow Leopard 10.6.5
iTunes 10.1 (if you have neither, select the Apple icon in the upper-left corner of your screen and click "Software Updates" to download the latest software.
AirPrint Activator [.zip]

Note: Netputing has removed the original file for this hack, AirPrint Hacktivator, per Apple's request. Airprint Activator accomplishes the same thing without breaking any of Apple's rules. DownloadAirprint Activator [.zip] instead. 

How to proceed:

1. Copy the AirPrint Activator software into your Applications folder, then launch the app.
2. Toggle the switch to "On."
3. Enter your admin password.
4. A window will prompt you to add the printer you want to use with AirPrint.
5. The hack will launch the Print & Fax utility in your Settings folder, and you'll be able to perform the add-printer task here.
6. And you should be ready to start printing!