Crafters are always looking for great supply resources. Here are a few places I like to shop:
JOANN'S - this one is a given. They have a great fabric section, their online site is helpful and they love to email and snail mail coupons. Plus you can usually find some pretty good deals in their clearance sections.
MICHAEL'S - another given. Huge selection of things in stock, special order and usually some really good stuff on clearance. The website offers tons of project ideas, inspirations and instructions. The only problem I have is that you can not order supplies directly from their online site; the only online ordering I have seen is from MiDesign which is Michael's more specialty design department. Lots of email coupons and they even have a smart phone app.
WALMART - this one depends on the store. Some have pretty nice craft sections offering some of the same products as craft stores but at somewhat better prices. My local store has an ok fabric department and then small departments for jewelry making, scrapbooking, needle crafts and yarn crafts. I do like the clearance and $1 items.
DOLLAR STORE - you have to be kind of picky when you use supplies from a dollar store. You can usually find some good deals but don't expect to find designer anything. I like them for vases, baskets, basic supplies and dishes for gift platters.
AMAZON - love Amazon.com because I can usually find a ton of things there to blow my money on. The huge selection of crafting books and supplies make it easy and relatively affordable to try a new craft. Plus, which the Prime feature, you can get free shipping on quite a bit of what you are looking for.
ETSY - there are so many supply vendors on etsy that it is easy to find someone you will want to work with over and over. I get a lot of my hair bow supplies from there, as well as any other supplies that can be hard to find and really expensive going through other options.
EBAY - yes, ebay. This is usually not one of the first places I look, but you can find some good deals there for supplies for upcycling projects. Huge selection from a wide variety of sellers. I am extraordinarily picky when it comes to using ebay though and will not shop from anyone with a rating less than 98% positive.