May sell my iPad

I have a 3rd Generation iPad (64GB and 4G). It comes with a smartcover and apple keypad. I have been pondering selling it, because I am not able to get the level of productivity out of it that I would like. Thus, it has mainly been a consumption device that I use to check email and the internet. I am also thinking about purchasing the Surface Pro. So, the question is: If I were to make efforts to sell my iPad, where would be the best place to post?