Here's a pretty cool free app from Sherwin-Williams. You can upload an image to find the paint colors and it also has coordinating pallets. The best part is it that it doesn't only tell you the Sherwin Williams color but the RGB colors.
I can totally dork it out and spout off RGB breakdowns on the go now! (Seriously though, this is great to build color combos for websites/blogs, etc)
Click here for ColorSnap from Sherwin-Williams.
Update: If you like Benjamin-Moore, theirs is out at the Apple App Store too!