Photographs are a critical component of your eBay listings; they can literally make or break your auctions, so it’s important that every item you sell is photographed in a way that both flatters it and clearly discloses any flaws it might have.
One way to bathe a subject in soft, even lighting–particularly useful for highly reflective subjects such as jewelry–is by using a simple light tent. The object is surrounded by a translucent material that is lit from the outside. The starting price for small ready-made light tents is right around $100. (Check out one here.) These are generally little white nylon tents that fold into a carrying case for convenient storage. Very nice, but way too expensive for the average eBay seller.
The links below describe ways to construct a variety of light tents, from the simple (plastic gallon milk jugs), to the more complex (Plexiglas cubes). They may not be pretty, but they serve the intended purpose and the price is definitely right.