I found this over on the Duct Tape Marketing Blog:
Adobe Labs released a very fun and useful tool for anyone that would like to learn about combining colors or creating what they call color themes. The tool is called kuler. (Requires the latest Flash player to view)
kuler is a designer playground and community that allows anyone to create color combination palettes and publish them for the community. Voting happens and the best palettes rise to the top under the “most popular” tab.
On top of being a very cool app, any business owner can go and find professional grade color combinations that can help set the mood for any print or online project. Need to know what subtle accent colors might go with your 2 color logo but still have trouble picking out what shirt and tie go together? Visit kuler, go through the popular combinations, and click on one that contains your base colors. The tool then gives you all information you might need for RGB, CMYK, and Hex settings.
Professional designers, or those that play them on TV, will love the fact that you can download the themes right into CS3. You can get the kuler release notes from Adobe Labs. If you really want to stay on top of color trends, get the widget for Mac users at MacUpdate
And just when you thought you were having too much fun with color: Check out this tool that allows you to upload an image and let the tool suggest some colors you might use as accents. Color Palette Generator