A new service to turn your iPhone images into postcards was announced by ECCE TERRAM. Using Photo2lab you can select an image stored on your iPhone, add an address from your contact list and send the image as a postcard. Prints and mini books will also be options.
ECCE TERRAM say it should be available soon after the iPhone SDK is released in February.
As someone who takes a lot of pictures with my iPhone I have to say I am looking forward to trying out this service.