I just took a quilt class and the instructor suggested this site:
http://www.thousandsofbolts.com. You can look at a fabric, then click on the COLOR MATCHER icon and it gives you all sorts of choices as to what would match. These are all high end fabrics at about 1/2 price.
I buy fabric where ever, but the suggestions you've already received are great! I love the Moda charm packs, vibrant colors all matched.