Yes, eBay was what I was thinking. You can do a search and/or completed search of each item and see what it's potential is. Keeping in mind that you don't want to list a book if there are 20 other copies of the same book not selling. You also reach potential bidders from all corners of the world.
Depending on your area and population, you could consider a live auction, leaving the work to someone else, but it also takes from the profits. You can also consider an estate/garage sale.