http://www.daddys.com
Daddy's Junky Music
If your near on of their locations these folks are the cat's pyjamas when it comes to used gear especially on the pricing. I got a used padKontrol there for 50$ I turned around and after using for 2 months sold for 100$. If you aren't blessed enough to be in the northeast, then they do happen to ship and the price for shipping is listed on the items which is pretty cool, rather than having to add to cart and nearly finish the order to figure out cost. They are definately heavier towards the traditional instruments but you can certainly find all kinds of stuff.
Check em out though, great resource.
