Usally the first place I post things for sale is on forums I am on. Next is craigslist, then sometimes I resort to ebay. Ebay is usally my last resort as I usally get the least ammount of money for a item, but have been surprised before and got more than I was expecting.
I have for the most part had pretty decent luck with craigslist. Not everything sells. I have had several people who call and set up a day/time to come look at or buy a item and then never hear from them again. That gets a little frustrating.