I love to sell things on eBay. Selling on eBay helps me get rid of old things I don't use anymore and gives me some extra money! Here are some ideas of things to sell around the house.
1) Old Electronics
This includes old cellphones, computer parts, laptops, ipods, etc. This is probably the top seller as most old electronic devices sell at a high price. Old unused laptops are pretty lucrative depending on the model and how old it is. Old video games and DVDs also sell pretty well. When I decided to sell my Nintendo DS on eBay, it sold super fast and at 90% of what I paid for it. The video games that I had for my DS sold like hotcakes. If your going to sell old DVDs and video games I would also try listing them on Half.com as well. Make sure that the DVDs that you list are original DVDs and not bootlegs. They don't allow selling bootleg DVDs on eBay, or anywhere else for that matter.
2) Old Clothes and accessories
Do you like to wear name brand clothes? If so, most likely most of those clothes will eventually fall out of style as new styles come in but you can still sell them on eBay. People are always looking for name brand clothes and accessories on eBay such as GAP, Banana Republic, name brand jeans, Nike, etc. One especially big seller are name brand purses, those always go for a high price as long as they are in good condition. When you list you clothes on eBay be sure to be perfectly honest about their condition. Put on the listing if it is pre-owned or not, how worn it is, if it is faded or not, damage to the material, etc. Put down the exact size of the clothing so the buyer knows if it will fit him or her or not and if you have the time I would also put down the exact measurements; bust size, shoulder length, waist length, etc.
3) Old Books
I would suggest listing old books on Half.com as I have had more luck selling old textbooks there rather then on eBay. If you paid full price for the book, you won't get all of your money back but you can still recoup a percentage of what you paid depending on how popular the book is.
4) Anything you can find
Almost anything will sell on eBay really. If you can take a picture of it and you think it looks nice and it can be shipped then it just might sell.