http://bg.battletech.com/

Its now being ran by Catalyst Game Labs. From what I've heard its been making a fairly strong comeback the last few years, though not really having an idea of where it was 15-20 years ago and how far it dropped, I don't really know what that really means. Seems to be a decent group of players in Phoenix when I was down there. But where I'm at now I'm really the only player, but where I'm at now they pretty much only play 40k, so its not exactly a diverse set of people, its also an area without a lot of people.