Here is probably to date the be all and end all of one-stop shopping
location for things: big things, little things and everything in-between,
fast friendly service.  I order late at night (11 p.m. EST) and usually
get the stuff in the next days UPS, but I'm only located one-half state
away from their warehouse.

The index is mind boggling.  If you are a purest, and prefer to turn
your own ceramic for the spark plugs you are building, this is the
place.  Low order dollars, and smaller amounts of an item.

The selection of drive belts, chains pulleys and connectors will keep
anything running for years.  They also have laminated nylon belts;
these are not affected by weather and stay tensioned almost forever.

  http://www.mcmaster.com/index.asp

I do the repairs and restorations on the Kemp Bros. Model City at the
Capac Historical Museum, Capac, Michigan.  It is a 40-foot long
operating model city that was built from junk and bits and pieces
almost 100 years ago and toured the world till World War Two.  Lots of
belts, chains, pulleys and "I don't knows" to keep things moving in the
City.