Photo printing is supposed to get easier when Air Print hits iOS 4.2 any time now. For those that either have older iPhones that aren't iOS 4 friendly or you're too lazy to update your OS, the Bolle BP-10 is the printer for you.
The BR-10 is compatible with all iPhones all the way back to the original and delivers standard A6 4"x6" prints that can be either one photograph or a collage of several. Bolle's iPhone app handles all of the settings and printing responsibilities; just tell it what to print and go. The BP-10 is pretty spendy at $192, but with no current competition in the market (save Air Print, I suppose) you're gonna pay a Apple-sized premium for this device.