CraftIRC is a Bukkit mod that intergrates an MC server's chat with an IRC server essentially allowing conversation between the two forms of communication.
Could be good to get more people on the IRC and cross communication between BoN MC servers via IRC.
All that would need to be done would be to intergrate multiple MC servers to the same IRC channel.
Cross servers eh? Might get slightly confusing. Should look at changing colour of players names to distinguish whether or not they are on the same server as you.