There are a variety of workstands available, from about $30 to over
$130.  Look at the mail order catalogs for photos showing the different
types.  The type with a clamp that holds one of the tubes on the bike
are the nicest and easy to use.  Park has a couple of models, and their
clamp is the lever type (pull the lever to lock the clamp).  Blackburn
and Performance have the screw type clamp (screw the clamp shut on the
tube.

If you have a low budget, you can use two pieces of rope hanging from 
the ceiling with rubber coated hooks on the end - just hang the bike
by the top tube.  This is not as steady as a workstand, but will do
an adequate job.

Some parts © 2009 Advameg, Inc.