Here is an interesting tool I stumbled across called Color Schemer for dealing with color (obviously) that I think would be nifty for us to implement something similar within inkscape.
Here are a couple screenshots in action: http://www.colorschemer.com/images/v3screenmain.png http://www.colorschemer.com/images/studioscreenharm.png http://www.colorschemer.com/images/studioscreenmixer.gif
There is an online version too, which has the basic functionality and we can probably view source to get some ideas from. http://www.colorschemer.com/online.html
My thought is that since we now have swatches, a “utility” like this would rock for knocking together good harmonious swatch sets with great ease. Just my .02

-Josh