ColorBlender is a cool Ajax-y service that suggests an entire palette of colors for you based on a dominant color that you enter (using RGB sliders). I’d still prefer a great visual designer come up with color ideas, but if you were on a budget and if you didn’t know the first thing about how colors complement each other, push forward, recede back, are cool or warm, etc., you could do worse than consulting this tool to put together a pleasing palette for a website.