I have begun development of a new site, TradeUps.net, where users will be able to barter with those in their geographic vicinity with the help of tags and Google Maps. It's still in its infancy, and the core components haven't even been written yet, let alone tested. I don't even care if it's already been done before -- it's more of a learning experience. I'll be journaling its development occasionally, starting today.
I first got the idea for a barter site when I read about One Red Paperclip, wherein a blogger trades a large red paperclip for a cool fish-shaped pen, which he trades for, [long chain of other trades] which he trades for a house. It occured to me that bartering can be mutually beneficial, and occupies a niche in commerce and trade that can't be fulfilled by monetary exchanges. Trades can be mutually beneficial in so many ways. For example, I may have a printer cartridge I don't want to throw out and can't sell -- best to trade it for, say, a couple extra reams of paper someone has on hand. This typ of exchange doesn't fall within the traditional framework.
The idea is that users can register items they want and items they have, along with tags and descriptions. Each user also marks a point on the map where they would feel comfortable meeting a stranger to trade. Then, when a user does a search for a particular item that someone else has registered, it shows up as a pipoint on the Google Maps-based interface. Users are free to contact each other outside of the site.
My site is starting small, just within the Charlottesville area. If it spreads, that's cool, but if it doesn't, it'll be a nice playground. My first real web app!