Google's Cloud Print launched in January. Unlike Apple's AirPrint, you don't need an HP ePrint printer to use it. Previously, you "connected" a local printer to Google's Cloud Print service by installing Google's Chrome browser and enabling the functionality in the browser. That PC had to be running, of course,
The functionality doesn't require the printer to be attached by USB cable to the computer. It works even if the printer is a network printer. It was originally believed that AirPrint would offer the same type of service, meaning that it would not require end users to upgrade their printer to use it (there are ways around this limitation, however).
In addition, however, Apple's AirPrint requires the iDevice and printer to be on the same network. Google's Cloud Print is truly that: printing through the Cloud back to your printer. You could be miles away when you print those pages.
HP said that all ePrint printers and all-in-ones now support Google Cloud Print.