Airprint is a new feature part of Apple’s IOS 4.2.1 that allows you to print from your IOS device to an airprint compatible printer (see list below).
For an IOS device to be able to print to this printer via Airprint, the printer and the IOS device needs to be connected to the same WiFi network. Printing from PC and MAC seems to work easily for me, but printing from the iPad caused problems when I tried to print, and select a printer, no printer was found.
At work we had a Cisco wireless network, and eventually to get it to work we had to enable a feature called “Multi-Cast Forward” on the wireless router. All 3 of our printers were now discoverable and we can print via Airprint.