Startup Idea : One Man's Trash

Have you ever heard the quote One Man's Trash is Another Man's Treasure. Well I would like to turn that idea into an app. I am not really sure where we could make the money with it. Probably via ads once the app blows up. Basically we need an app where people can get rid of things that don't need anymore. This app would be for giveaways only. Kind of like the free section of craigslist. Is there something already like this? If there is, could we take it to the next level. I would love to work with some people on this idea. I am not much of a developer but I have other marketing skills.