Thanks for the reply
Try this page for background: http://www.hp.com/sbso/printing/mac/hp-airprint.html
I suspect Apple's airprint uses the same mechanics as HP ePrint enabled printers. The print button on the iPad, I believe, actually sends an e-mail to the HP printer, which instantly prints the document. Prior to the os release enabling this function, to print from an iPad you had to attach the document to an e-mail sent to your address, go to your desktop, fetch mail, and print.
So how to use a linux box on your lan to instantly print an e-mail. Again thanks for the reply.