Goodwill Computer Works.
Everything except Microsoft Office and the Commodore Modem is shrinkwrapped, brand new in box.
They were arbitrarily priced from $2-$6 each. I pretty much cleaned them out of shrinkwrapped Mac software. I did turn down some non-shrinkwrapped software because I don't know if the boxes are really complete or not.
For old software I look at thrift stores, Goodwill is ok for old DOS games once in a while, and Village Discount Outlet thrift is good for mac software once in a while.
I'm not sure if I want to open any of the boxes...
Actually I have two shrinkwrapped HyperCard Dev Kits. One is for sale if anyone is interested.