Neat idea. When designing something, the search for a fitting color palette is always an obligatory important first step. Sites like Adobe kuler help you here insofar as they offer the ability to share beautiful color palettes between users.

Mondrianum goes one step further in that it allows to access the kuler palettes directly from the Mac OS X system-wide color-picker. Which means that the colors are available from (for example) iLife, iWork, Photoshop, Coda, CSSEdit, and more.

Mondrianum is 10.5 only and can be found over at Lthoglyph Software.