I organize my fabrics mainly by type - Moda Marbles; Kona cottons; batiks; Asians; patriotic. If I buy several pieces of fabric from the same line, I try to keep them together. And, I also put all my fabric on these plastic holders that I get at
http://www.polarnotions.com/. They are very stiff plastic, so don't bend. That way, my fabric closet is like a fabric book case.