Depending on direction you are coming from -
I LOVE The Round Bobbin in Ambler.
There are some that have closed over the last year or so; you might want to either call ahead or check for a recent web posting.
Steve's Sew & Vac in King of Prussia is okay - as the name would lead you to believe, they focus on machine sales, but do have a decent selection of fabrics.
Pottstown Sewing is more embroidery focused, but have some fabrics.
Sew Smart in Doylestown didn't flip my skirt; Byrne Sewing (listed in New Britain, which kind of runs together with Doyelstown) was better.
Depending on direction you are coming from, there are two in Endless Mountains that I love. One is Shore Sisters (in Wysox) and the other is Endless Mountain Quilt shop in Tunkhannock. Those are 3-ish hours away...