Big Huge Labs create anything from a photocube to trading cards.
FotoFlexer allows you to directly upload your images to sites like Facebook and Photobucket
Picasa offers photo editing in addition to its photo sharing (see below) capabilities.
Daily Shoot offers a new shooting prompt everyday. Go out, take a picture related to the prompt and upload via the website or Twitter.
Flickr a crowd favorite
Picasa Google's photosharing
Snapfish HP's photo sharing site