Printing wireless from an iPad - it's now a dream that has come true. Although be careful, there are only a handful of printers that are compatible with Apple's nifty AirPrint.
All of the 12 models are from HP, seven of which are compatible out of the box, those seven are:
• Photosmart e-AiO D110
• Photosmart Wireless e-AiO B110
• Photosmart Plus e-AiO B210
• Photo Smart Premium e-AiO B310
• Photosmart Premium Fax e-AiO C410
• HP ENVY e-Aio D410
• Photosmart eStation C510
The remaining five require a firmware update to jump to AirPrint compatibility:
• LaserJet Pro M1536dnf Multifunction Printer
• LaserJet Pro CM1415fn Color Multifunction
• LaserJet Pro CM1415fnw Color Multifunction Printer
• LaserJet Pro CP1525n Color Printer
• LaserJet Pro CP1525nw Color Printer
But, if you're printing from a Mac, there is always the AirPrint Hacktivator program which will make AirPrint work on pretty much any printer...