Update: The clever fellows over at Netputing bundled the files together with a snazzy install/uninstall button to produce AirPrint Hactivator, which takes care of all the under the hood business for you. The same caveats apply: remember that you are installing obsolete/beta system files, use at your own risk, and if you'd prefer a supported product there are options.
Mac OS X 10.6.5 was released yesterday, and one of the features it was expected to bring to the table was support for AirPrint, a new feature in iOS 4.2 that was supposed to enable wireless printing from an iPad, iPhone, or iPod touch. Unfortunately, whether it's because of technical problems or patent trolling, Apple pulled support for this feature at the last minute. In its current incarnation, AirPrint in iOS 4.2 will now only work with specific printers that come with AirPrint functionality built-in... and you probably don't own one of those.
iOS 4.2 hasn't been officially released yet, but some enterprising developers, Steven Troughton-Smith and Patrick McCarron, have already found a way to re-enable AirPrint functionality in Mac OS X 10.6.5. Apparently, three files from earlier developer builds of 10.6.5 were removed or altered for the final public release, and it's these files that are essential to restoring full AirPrint functionality. Click "Read More" for a walkthrough on how to enable AirPrint.
The usual caveat: This procedure involves a moderate degree of peril, and TUAW cannot help you if you mess up your system. Proceed at your own risk.