fabric.com has a good selection of extra-wide fabrics. Whites, tone on tone, prints, flannel, muslin... I think their prices are reasonable:
http://www.fabric.com/quilting-fabri...Source=LeftNav
sewbatik.com has a nice selection of extra-wide batiks.
http://www.christianlanequilters.com/widebackings.html sells only FatBacks (queen-size backings) and extra-wide yardage. Good selection.