Traditional color choice tools tend to show the full RGB / HSL etc color space. This, to me, doesn't help when trying to find interesting combinations. Other approaches, such as on Adobe's Kuler where you have the ability to apply a triad while exploring a color space, also don't really seem to produce pleasing results for me. Simple linear gradients between two colors also don't seem to have enough movement in there - but that could be a choice of the kind of color blending used, I suppose.
Anyway, taking visual inspiration from Goethe's color triangle, I made this tool to explore some other ways of displaying color choices, and to see what the results might be.