On Ebay from my experience I would say that used DVDs and video games are insanely popular. Books, just because there are so many, are also a big seller even on Ebay but nowhere near the volume that Amazon does. The volume that amazon sells of books is just absurd!
Dinky little things are incredibly popular on Ebay. Specifically things that weigh between 1-3 ounces, and ship direct from China. Type in any search term with lowest buy it now...your eyes will go numb sifting through it all before you find someone selling an item that's not mass produced, directly shipped from China.
Junk that is shipped from china is much less common on Amazon. Amazon is more well known for suckering book buyers into overpaying for overpriced gimmicky items like inflatable pet beds and obsolete as seen on TV items.