One of the most difficult things for me is color coordination. Picking the right color combinations for the right task or job at hand is not all just having a good eye. You can mathematically get the right color sets. If you are not a designer this can be daunting and can make your application or website be a complete flop. I know a few online sites such as http://www.colormatch.dk and http://colorblender.com can help you make the right choices. I wanted to throw a spotlight on Adobe Kuler. It has a variety of delivery methods to the user. An Adobe Air application, a Mac OS X widget and http://kuler.adobe.com are all available. The website provides an image upload where color combinations whether it be analogous to complimentary colors. Upon arriving at the right color theme set it will give you a full complement of HSV, RGB, CMYK, LAB, and HEX information. The widget and Adobe Air application are both great for viewing and downloading user created themes.