I have a multigym that cost about $3500 and would like to sell it if
possible, otherwise I will give it to charity.  At first I thought of
e bay, but that looked like a bad idea based on a review of completed
auctions.  This equipment is very heavy.  A good answer would give
specific internet sites that either buy used gym eqipment or sell on
consignment.  Alternately, are there productive internet sites for me
to list this piece of eqpt. for sale.

http://www.playitagainsports.com/playitagainsports/myheadline.asp?S=7312&P=3979&PubID=4332

I know someone who used e-bay to sell some used gym eqiupment and was
pleased. The person was local, so it didn't matter that it was heavy.
You can always reserve a price, so you don't sell it for less than you
expect. you may also contact a local gym to see if they're interested.
High schools all over are in desperate need of equipment for their
sports teams to use. Hospitals also use equipment like that for
rehabilitation purposes. When it looks like it's just too much fuss,
charity is giving back to the universe , they will usually pick it up
free of charge, and the karma dollars just keep rollin in. Good luck.