There are many, many online sources of gingham, here are just a few and what they have to offer:
Gingham shirtings - from Gorgeous Fabrics
100% linen gingham - from Denver Fabrics
Quilting weight gingham - Above left, Darla collection by Tanya Whelan, from Fresh Squeezed Fabrics. Above right, Sweet Pea by Moe3 from Down Shadow Lane.
Gingham seersucker - from Fashion Fabrics Club, 97% cotton, 3% lycra,
Organic gingham - from NearSea Naturals. Above left, blue and white organic cotton jersey. Above right, rich brown organic 60" cotton woven.