I use Amazon for my books all the time.  Its nice because you set your price and just wait, but it sucks bc they seem to be taking a lot of money from you.  I think they took like $12 on my last sale which was ~$110ish.  They also have a weird payout period, where they only give you your money ever 2 weeks or something like that.  Also, if you do sell from there, make sure you get a delivery confirmation.  I had someone claim that I didn't send them their stuff.  :-P