Check out Queen Anne & Magnolia Paints for a good selection and information on paint. The staff is certainly more knowledgeable then those you'll encounter at a Lowe's or Home Depot. When I painted my place a few years ago they were great in helping me understanding how various paints and colors would look and react to different light and uses within my place. This alone was worth the visit to Magnolia Paint.
The one downside is if you have a specific brand of paint you want they may not have it. It is a fairly small shop. They still have some high quality brands available.