4096 Color Wheel — A very nicely done and pretty color wheel showing 4096 colors. Move your mouse over the wheel to instantly find the correct color for your project. Then click to have access to the variations of the color you clicked on. Simple and quick. ficml.org

 Color Scheme Generator — A nicely-done color scheme generator with support for contrasting, triad, tetrad, and analogic color schemes. Also shows what your color scheme will look like to color blind people. wellstyled.com

 ColorBlender — Blend two colors and generate a color scheme with those colors. Very useful color tool for palette design. colorblender.com

 ColorMatch Redux — Choose a good color scheme then export to ACT, AI, or plain text as RGB or Hex. Also allows you to type or paste in a starting color which is very useful. stylephreak.frogrun.com/cm.php

 ColorSchemer — A handy tool for exploring different color schemes. Shows the RGB and HTML color values and lets your lighten or darken your color palette with a single click. colorschemer.com/online.html

 Colour Lovers — A site that "monitors and influences color trends". colourlovers.com

 HTML Color Codes — Just like it says, a simple chart of web-safe HTML color codes, with hex HTML color values. html-color-codes.com

 Image To Color Palette — Extracts a color palette from any online image. Simply supply the URL of an image with a good color palette, and it will find the actual hexadecimal colors in either dull or vibrant variations. Very impressive!  degraeve.com/color-palette/

 Kuler.Adobe.com — Check it out!  A fantastic color scheme explorer and creator. Vote on other users schemes. Very slick, but entirely Flash-based.  kuler.adobe.com

 Steel Dolphin Color Scheme Tool — Another very handy color scheme generator that does not require Flash even though it has pretty advanced controls and sliders. Supports several different color palette options like monochromatic, complimentary, split complimentary, and even double contrast.  steeldolphin.com/color_scheme.html

 YaflaColor RGB - HSV Conversion — Convert HSV to RGB and back and instantly see the triad and other complementary colors.  yafla.com