I think this is a good technique for finding colors, particularly if you are doing something with a lot of photos. I used this technique on the Twin Cities site that got shot down, starting with a nice sunset photo.

I also usually check out Return of Design’s Color Palette blog when I am starting somethign new, which hasn’t been updated much lately and keeps going down.

The guys at Firewheel also have a color palette widget.

I usually try to have a balance between warm and cool colors first and foremost but I try to do layouts in a color-agnostic way, just getting things down on the page first, then adding/tweaking color.

I don’t know much about Color theory, other than the usual complementary color deal. Sometimes I think ignorance is a good thing. Eat the rich.