The Bitcoin-OTC project is a marketplace for people to conduct over-the-counter trading in bitcoin. It is located in various IRC channels on the freenode IRC network:
IRC Web #bitcoin-otc
IRC Web #bitcoin-otc-eu
IRC Web #bitcoin-otc-ru
IRC Web #bitcoin-otc-uk
Trading in the market is facilitated by the gribble bot, which takes care of maintaining the outstanding order book, as well as a web of trust user rating system. All trades are conducted between users directly, without any intermediation by the marketplace.
The source code for all the related software, including bot plugins and the website, is open, and hosted on this github repository.