I shop primarily online as I live in a rural area with no quilt shops. I buy most of my fabric from a few trusted Ebay sellers and usually will only buy via auction...great way to save $$$. I also shop at:
connectingthreads.com
whittlesfabrics.com
keepsakequilting.com
fabric.com
Of those Connecting Threads and Whittles are my favorites. Hope that helps!
~Peggy