The folks at Big Huge Labs have created quite a library of goodies that can interact with your Flickr account. I particularly like the Palette Generator (which works with or without a Flickr account).
As you can see, it works better from photos than it does from illustrations though. It seemed to have trouble locating the pinks and reds in my work, but that may be because of all the white space that makes up the file. Still, if you want to generate a rough palette for an illustration from a photograph you like, this is a quick and fun way of doing it.
