Check out filetopia. Lots of DC trading/sharing going on there. It is like Napster style file sharing (but for all file types), and IRC style chat, and everything is encrypted using strong crypto and public keys. Very nicely made. You can even run a ratio FTP-like server so people upload etc. It's cool, check it out at http://www.filetopia.com

The more people who use it, the cooler it will be.