In addition to fabric, Ebay is a good place to find stuff like stretch lace, elastic trim, and novelty tapes – grommet tape, eyelet tape, d-ring tape, etc.
Some of my favorite Ebay shops for trims:
Kathy’s Lace and Elastic Outlet – Nice selection of stretch lace and fancy elastic trim.
Fabric Fanatic – Lace, elastic, and lots of assorted trims.
Mix and Match – lots of cute buttons
And on Etsy:
smarmyclothes – novelty buttons, trim, and sometimes fabric
And elsewhere on the net:
Lace Heaven – Wholesale prices, with no minimum order. Really good selection of both stretch and non-stretch lace, as well as other embellishments.
Lace For Lace – Wholesale supplier for lace, organza, and more.
CheepTrims – Wholesale supplier of trims, with a good selection of the harder to find stuff. They have a minimum order ($75, I think), and their stuff comes mostly in bulk. (BUYER BEWARE: at least half a dozen girls on my street team have had fraudulent charges made on their credit cards after ordering from CheepTrims. CT does not seem to have done anything to remedy the situation, as the problem is still occurring. Please be wary of this when buying from them over the internet AND over the phone.)
Studs and Spikes – Pyramid studs and spikes, and other hardcore embellishments.
Crust Punks – More studs and stuff. They have a fabric section, but please note that prices are PER FOOT (i.e. not cheap).
M&J Trimming – Lots and lots of trims and other embellishments, notions, etc.
Cream City Ribbon – Cream City Ribbon is the only producer of 100 percent cotton ribbon in the U.S. Eco friendly!
Craft Queen – Specializes in ribbons with more than 500 available. Also a wide selection of buttons, flowers and general scrapbooking supplies.