I use a 5 pound scale. It's nice and small and weighs in small increments, which is nice if i want to estimate the amount of grams in a piece of jewelry. (I don't think I could use it as a definitive weight on jewelry without checking it regularly, etc.) On the rare occassions I have something bigger, there is a scale at the post office, or there is always my digital bathroom scale (half-pound increments) for a rough idea of weight.
If you do sell small things, having a tare setting is nice. Then you can put a container on the scale, tare it, and drop beads and other little things in.
I bought my wonderful little scale used from another ebay seller who mentioned she was selling one on another board, when we were talking scales. A lot of people get smaller scales then realize they need/want bigger ones. This includes the free ones from stamps.com. But I was pretty sure I just wanted a smaller one, and it's been great for a couple of years!
Ol' Will Knott has always been highly recommended for scales over on the ebay stores board. He has(had?) an ebay store, but here is his website: http://www.oldwillknottscales.com/