Michael Miller Cotton Couture has the most beautiful colors. It seems when I have fabrics to match and go to the solids color wall of my local shop, I always end up choosing Cotton Couture without seeing the names - just the colors.
Art Gallery Pure Elements is another solid with beautiful, saturated colors. I bought two small bundles last year at the Quilt Show in Houston and still haven't had the heart to break up the little stacks.
They are just so pretty. I think the Art Gallery solids are the best quality fabric - very, very little fraying and a tight weave - but at my local shop they are just $1 less than prints but some quilts are worth it.
For regular quilts, my first choice of solids is Michael Miller and then Moda.