Adobe Kuler has a quick and easy tool to create color palettes.
Color Scheme Designer is a very useful way to create a custom color palette.
COLOROTATE is a site that has a 3D color chooser. You can also browse color palettes and they even have an iPad app.
Checkmycolours offers a service to check your web site’s contrast ratio, brightness difference, and color difference.
COLRD is a place where you are able to extract colors from images and create color palettes. After you go to the site click on “Create” button at the top of the screen to begin.
Contrast-A has an application that allows users to experiment with color combinations, examine them under the aspect of accessibility guidelines and to create custom color palettes.