AirPrint is one of the most welcome additions of late to iOS 4.2. Unfortunately Apple removed the ability to print to shared printers. Fortunately, creative software developers such as Ecamm have created Printopia as a solution for those of us with networked or shared printers.
The simplicity of this Preference Pane is amazing. It takes less than a minute to setup and use.
The only problem I found was when installed on my server I had to open port 49195 in my firewall for it to work. Now all is well again. I can’t recommend this $10 piece of software enough.