Black, Gray and White

Often designers tend to overlook the usefulness of the neutral colors black, gray and white. These colors harmonize with most other hues and are an excellent way to offset the visual effects of two strong colors.

This web site uses predominantly black, white and grey with touches of orange.
http://www.hillier.com/skills/view-cat/architecture

This site relies on grey, black and white with splashes of color (to make the cars stand out). Notice how the colors (e.g. yellow and red) are very striking when combined with the monotone colors:
http://www.miniusa.com/#/MINIUSA.COM-m

If you've examined the color wheel and pondered the merits of achromatic colors without coming up with a satisfactory color scheme, try this "random" color selector:
http://www.colorsontheweb.com/colorwheel.asp
I had a lot of fun with this!

The above site also has some great information about color. Here's the main page:
http://www.colorsontheweb.com/