Certain magazines are easy to sell on eBay.

Magazines.  Preferably old ones.  My best shot were rock and roll/hard rock/heavy metal magazines.  I collected quite a number of them in high school and my early college years--classics like Metal Edge and Hit Parader to name a few.  Make sure all of the appropriate posters are intact (of, if they're not, make sure to list it correctly and they are not intact.)

The condition of the magazines is a must-know for most buyers.  If the bindings are loose or the corners are bent, make sure to list it that way.  Even take pictures, as proof.

These magazines were the best for me, and the average price I sold them were around $12--but there was a few I sold for much more.  I've sold magazines internationally too, from France, Germany, even Japan.