There are several ways to get your own IRC server.
there are some easy windows servers such as conference room (
http://www.webmaster.com)
Windows ircds are usually not very good and not recommended for irc networks, most major irc networks develop their own server and services, undernet use ircu (
http://coder-com.undernet.org) and use the services gnuworld (
http://www.gnuworld.org)
There are many other types of servers and services such as unreal ircd, bahamut, hybrid and many more.
To run your linux (or freebsd) irc server you need an account on a linux machine, you can buy ircd accounts from most major shell providers, these let you run you own small ircd server and link to some minor networks, to link to any of the major irc networks you need a dedicated machine running on a major connection with good firewalls due to all dos attacks, the attacks against my undernet server sometimes hit over 1Gbps
You can buy a ircd account from companies such as kirenet.com, lomag.net, sh3lls.com, and many many more, just search for "ircd shell" or something simular on google.
Good luck.
