Ez of Creature Comforts recently posted about this fantastic (and easy) version from DeGraeve. You simply copy the URL of the image you love into the top field and voilà - you've got a palette with 'dull' and 'vibrant' categorized colors.
If you're interested in finding paint shades to match your image, try this generator that Gregory posted a while ago. You take the results and convert them to CMYK using a color conversion calculator, then take the numbers to your local paint store.
Got any other color palette generators we should try? Recommend them below.