I use to sell on ebay. ps2 memory expansion cards use to be a hot ass seller on ebay. you can get them direct from the manufacturer cheap as fuck at
http://www.hkems.com/ buy em for 4-5 bucks and flip them for 20 dollars. They don't check for Tax id etc. I think the min order is 20 or 50, im not sure its been so long.
I found information is also a hot seller, where to buy shit wholesale guides, hacking guides etc.
I also tried to sell porn dvd's and tapes but every other person and there momma is selling bootleg shit for cheap so its hard to sell em if you have legit copies.
Jewelry is a hot seller on Christmas and Valentines day, i got a diamond wholesaler source I found off ebay. 1 carat diamond solitares for 200 a piece, I clarity G-H in color. I use to buy them in pairs, get them set in earrings and sell them for 1000-1500 like hot cakes around Valentine.
Go for the gaming shit on ebay, from personal experience thats what sells the most