Every seamstress should be reading True Up. It's a blog dedicated to fabric! It will teach you all about different textiles from how to care for them, how they are created, where to purchase them (e.g felt shopping guide), sewing tips, etc. I've learned so much from this site. It truly is a fabric addict's dream come true.
True up also lists online fabric sales each week, often with codes for additional discounts. I can't say enough good about this blog.