So this idea has been passed around for quite a long time now. We do now have a Teamspeak 3 server available.
Now I should mention at this point, this is NOT a replacement for discussion over IRC/chat. IRC should still be the primary coordination method.
The Teamspeak server is to be more of a supplemental thing, mostly for general banter. If a group of #openttdcoop players want to use it to coop in other games, we can open it up for that on a case-by-case basis.
Server info available with the @teamspeak command in IRC.