Here are some of my favorite resources for the things I make. While I prefer to buy locally (as in I want it right this second), there are just some things that I can't get around here. I have scoured the web and found a few places out there that I want to share with you!
Seattle fabrics has a great selection of fabric for bags, backpacks, outerwear…and tents, if you’re into that sort of thing. Order their swatches, it will make it easier to choose the right fabric for your project!
Sailrite is a great place to buy fabrics and sewing tools. They specialize in marine applications (such as sailmaking) but there are a lot of great how-to videos for projects around the home. Their videos are well made and easy to follow, I highly recommend!
If you make bags, Strapworks is a great resource for all things...straps! They carry many varieties of nylon webbing (think backpacks), as well as good hardware (metal and plastic) at a reasonable price.
Making anything with grommets means needing grommets. Grommet Mart has a great selection beyond the standard Dritz grommets you can find at a local Joann Fabrics.
If you're local to the Chicago area, check out Vogue Fabrics in Evanston. They have a huge selection of fabrics for apparel. They do have a website and you can order online, but if you're local, check it out, it's worth the trip!