Looks to be a nice alternative to eBay for selling music instruments.
Main page: reverb.com
From their Why Reverb page:
Why Reverb?
Reverb offers the best variety of tools to buy & sell gear, and the lowest listing fees of any major site. As musicians and gear lovers, we work to foster a community and make Reverb the best place to purchase music gear online.
eBay is 10% plus a bunch of hidden fees (currency conversion, limited free listings/month, lock into PayPal with their set of fees, etc...) Reverb is a flat 3.5% - adds up!
Mostly guitars for now but worth checking out every couple weeks...