IRC. A meeting point for geeks and other animals.A favourite playground of the ScriptKiddies.
Popular IRC clients include mIRC (http://www.mirc.com/) for Windows, ircle for MacOS, and irssi for GNU/Linux (http://irssi.org), and ERC for Emacs.
Recommended servers and channels (feel free to add your own):
irc.FreeNode.net - #Object - All things Object Oriented. Any Language. Yes patterns too.
irc.FreeNode.net - #wiki - talk about wiki tech and culture
irc.FreeNode.net - #ruby-lang - A hangout of Matz, DavidThomas, et. al.
irc.FreeNode.net - #moin - MoinMoinWiki? official channel.
General server/channel-finding advice: The best way to find interesting IRC channels is to find references to them from websites. Just search for something you're interested in along with the keyword "irc". Alternatively, you might want to try searching for "Undernet", "DALnet", or "EFnet", which are the three major IRC networks. The website will list both a channel name and a net/server name - just fire up your IRC client and pick "Random <Foo>net server" or the equivalent.