The web has many digital tools for creating color schemes that are based on traditional analog design interfaces: color wheels, bars, and sliders. Probably the best-known of these is Kuler, but there are some good alternatives:

Color Scheme DesignerColor Scheme Designer is a tool that not only allows you to create arrays of hues using the techniques I’ve explored in a previous article, but it also allows you to simulate the same hues under conditions of color-blindness, see them used in a mock layout, and export them as HTML + CSS, a PhotoShop palette, or as a URL you can share with others.

0 to 2550 to 255 is a great way to generate close variations on a hue, or monotone color theme. (Uses Flash).

colllor is another nice color scheme creator, and colorhexa is an excellent color encyclopedia that tells you almost everything you need to know about a color, including generated CSS code examples.