The official Killing Floor IRC [Internet Relay Chat] is up.
Unfortunately there are not many people yet, but we want to change that.
Just connect to irc.synirc.net and join #KillingFloor.
If you do not want to get an irc client, you can use the online client in your webbrowser:
http://cgiirc.synirc.net/Recommended IRC chat clients (if you have never used one, but want to do so):