Give this app a color, get a scheme in return. Adjust your scheme using a color wheel, with controls for brightness, saturation and contrast for the more advanced users. Top it all off by seeing how your palette looks to color-blind users.
Color is complicated! Learn some of the common pitfalls of how we see, perceive and discuss color. A bonus: Instantly feel better about every stupid color decision you've ever made.
Excellent curated palettes. A great resource for color inspiration and keeping up on color trends. Every update includes the pic the palette is based on, for that extra dose of color inspiration.
Color tools for Firefox (and now Chrome, too!). A great supplement to the Web Developer Toolbar.
Color palettes straight from images. Unlike competitors, Color Hunter lets you upload your own image, use an image's URL, or search through tagged images, all in one site.
An excellent look at avoiding black and using other colors to enrich your designs. Like Van Gogh, Monet did amazing things for color. Don't let him down; read this post.
User-created palettes. Create your own and see how people like it, or just go and get inspired. Another great place to keep up on color trends.
A nifty tagging system and an API make colr.org a must-stop-at destination for any coders who want to mess with colors and color schemes.
A full-fledged community for lovers of colour.