I often have trouble coming up with good color palettes for my themes, icons, and applications. I think I have a good enough sense for what looks good together and for finding tones and hues that match the mood of said app, theme, or icon, but it always takes me hours to identify the colors on the color wheel or spectrum.
Last night, quite by accident, I found a solution to this conundrum that may make my life quite a bit easier. 
As I was resizing a bunch of photos (using my favorite little image manipulator Acorn) I accidentally dragged one on to the color picker. The image showed up in the palette a moment later and a little eyedropper icon was hovering over the image. I found that I could get that radiant orange from the poppy and the deep rich green from the trees and add them to my favorites (that little row of boxes at the bottom of the color picker).
Nature has a great palette, and I think I might be exploiting it more now that I have found this tool. Have you found any neat tricks for color selection?