Organizing a meetup through the internet with semi-strangers is like herding cats. I say we all take a peek at our friends lists when we sign on (under the TIGS group) and join a server another TIGer is on if the lag aint too bad. I know I've seen a few TIG people join my games from time to time.
Actually, putting up a TIGS Steam group event worked fine in the past, since everyone in the group gets a little "bing, we are playing TF2 now guys, come join us" popup.
Also, the game nights usually work out pretty well, too, from what I could gather.
We'd need someone who is admin in that group to do that though.
Essentially, if you wanna get a bunch of TIGS guys together to play games, your best bet is the Steam group and the IRC channel.