Useful Websites
Good source for historical and sci-fi costuming
Where all the anime costumers (cosplayers) go

Useful Books
Reader’s Digest Complete Guide to Sewing
Sewing techniques really haven’t changed that much over the last century so you can get this or other sewing books from a used bookstore for really cheap. (AJ’s is from the 70s, Judy’s is from the 40s, and we still get use out of them.)

Designing Apparel Through the Flat Pattern
This is a more advanced book but is invaluable if you want to get into drafting your own patterns.

SF Bay Area Fabric Stores 
Fabrics R Us
Unusual fabrics and cheap. Not good for natural fabrics like wool or cotton.

StoneMountain & Daughter
High end unique fabrics. Has specialty sewing supplies like horsehair canvas.

Historical costuming supplies

Five floors of fabric. They have amazing selection and amazingly expensive prices. Only go here if you’re desperate.

Mendels & Far Out Fabrics
Heard it has good fur selection; we’ve never been there though.

Lots of locations, best default shopping place. Check here before you go elsewhere.

Same as JoAnns but fewer locations