I'm fortunate in that I have several stores near me that carry good quality fabric, and a few of them run sales. Fabric Depot is a good one, they also have a website and as long as you buy name brand fabric (such as Moda or Timeless Treasures) you can't go wrong. There's also Craft Warehouse, which is a regional chain, and they occasionally have coupons and sales. No website, though. One of the quilt shops has a back room full of clearance fabrics. You could always check your LQS for clearance fabrics.
As an aside - this thread made me chuckle, remembering something my mom told me a few months ago. She's a beginning quilter, and persuaded my dad to stop at a quilt shop so she could add to her meager stash. He told her not to spend more than $5.00. I laughed out loud when she told me this - obviously he hasn't been in a fabric store since the 70's!