(Obviously, not "just" for the iPad
After its earlier preview, HP has started shipping the first of its e-mail-capable printers. The e-All-in-One D110a can print documents sent directly to its unique e-mail address, letting iPads and other devices without native printing support or even USB send images to the color inkjet. 802.11n Wi-Fi puts it on the local network without needing any cables beyond power.
I use Canon inkjet printers at home-hope they come up with something similar.