bighugelabs.com is always fun to play on - here's a new flickr toy I just found that creates a palette of colors from a photo you choose.
These are web colors, so it could be especially useful when creating your blog or website - especially if you have a photo banner and want to coordinate your background, font colors, etc..I end up doing this every time I change my header and have to go into Photoshop to manually select colors with the eyedropper.
I had some fun playing with this for our house last night too - using images of pillows and things to see what it came up with. I love the idea of using one item and planning your decor around it. For me its our white Bertoia diamond chair and the green/blue Anthropologie pillow that sits on it. Unfortunately it didn't really work with that image because of the wall and carpet colors - came back with a bunch of icky browns...that was a bad example, but you get the idea.