Online Image Editor - Ajax or Flex / Flash?
Ajax version would have to use something on the server processing the images, like the GD Library or ImageMagick. With flash you/flex you could do the image processing on the client side, and with Flash Player 10 you can take advantage of Pixel Bender for image processing. I guess it depends on the size of your images. I would be interesting to see a benchmark on some big images, flash vs ajax/php.
Good question.