Is there any way to print directly from my iPad to my wifi-connected printer? I am happy to purchase an app, but the only printing app I'm aware of seems to just let your ipad connect to a computer that is connected to the printer and effectively print through it.   

I'm looking to print from my ipad without the use of another computer.   Both the ipad and the printer are on the same wifi network (which is how I print from our laptops).

EDIT:  In my specific case, the printer is a Canon MP990.
iOS 4.3 now offer AirPrint.