We've blogged about Colourlovers before, but there was one feature we just discovered and wished we knew about before we painted our home "office"...
The site, which includes different tools for mixing and matching color palettes, has a feature that allows you to plug in a url for an image whose hues you particularly dig and have the image's color palette created for you so you know exactly what tones are included and how they work together.
We chose an illustration from John James Audubon, whose colors we thought would look lovely in a room. 
We then selected five of the 24 colors the site offered and created our own little palette.
Our only wish is that Colourlovers had a partnership with a paint supply company like Benjamin Moore which would then tell you which of their hues best match your palette.
[via Design*Sponge]
Image: University of Delaware

White Enamel Flatwa...
Sherwin Williams paint has a dumbed-down version of this idea. You can upload or select a photo and when you click on different hues it will match them up to one of their paint colours and suggest co-ordinating chips.
Not nearly as fabulous as colourlovers (of which I am one) but fun for quick room ideas.
http://www.colorofinspiration.com/?WT.mc_id=SWcom-COI-Blue