Well, Craigslist is mostly local, so you'll probably get a better price on eBay. On the other hand, you'll have to deal with the packing and shipping costs. On eBay you have a wide range of option to make sure you're happy with the results. You can set a minimum bid, a "reserve" bid, a Buy It Now price, and you can use the "Make an offer" feature.
First thing I'd just look around eBay to find out what kind of price to ask. Then I'd network locally. Women are great for that. Just tell two or three women in your life that you have this great converter you can't unload. Then, after a couple weeks, if nothing pans out locally, give eBay a shot.