Dancer IRCD:
CODE
http://freenode.net/dancer_ircd.shtml

This runs the Freenode Network

ircd-ratbox:
CODE
http://www.ircd-ratbox.org/index2.shtml

This runs the EFNet.

Both are damn stable and robust - can guess from the networks they run

Hope this is helpful to people who want to start their own IRC networks.

 Also checkout Unreal IRCD, this has to be my all time favourite, very easy to install and very easy to intergrate services.
CODE
http://www.unrealircd.com