Very slick web-based interface. Easy to use, many great effects.
FotoFlexer touts itself as "the world's most advanced online digital photo editor." On its site it offers "advanced effects previously only available to professionals using expensive software."
FotoFlexer was founded by Arbor Labs, a team of graduate students and alumni from the Center for Entrepreneurship and Technology, University of California at Berkeley (and just one MIT/Stanford alum too).