Amazon Supply is one-stop shopping for makers, hobbyists, and DIY aficionados. It gives you quick and easy access to thousands and thousands of items that might be tough to find in your neighborhood hardware store or Home Depot... Bearings, bushings, motion control components for robotics, tubing, all sorts of metal stock, seals and o-rings, scientific lab equipment, tools, abrasives, etc., etc. I did a search for bearings, which returned over 5,300 individual items... An impressive breadth of inventory is available all across the board.
Amazon Supply features industrial and scientific products from top-notch suppliers like 3-M, Mitutoyo, Norton, Dewalt, PanaVise, and many, many others.
Check it out... before you run all over town looking for just the right fastener, or copper tape, or some aluminum bar stock, whatever you need, take a look at Amazon Supply.
Update: For Steampunk art projects, Amazon Supply is a good supplier of materials, gears, etc...