LOL I never said I enjoyed playing anywhere, just that they exist in droves, depending on the time of day. I wouldn't recommend most of them, as their settings are all junk and the trolls rule the world since there's rarely admins around at odd hours.
It's safer to just ask me to toss a server up.
But they do exist. This is the largest clan that I know of:
http://www.thejawaclan.com/wiki/index.php?title=The_Server I don't care for their server settings, though. There are a few others, but I don't have links, they can be found on the tracker. Also, Jedi of Force [JoF] exists somewhere as well I think, but their stuff is all private and hidden and stuff.
Also @Matt: I'd still be contrary if the statement was less blanket, and said "the vast majority of activity is concentrated around MBII," considering there are still maps, skins, etc. coming out every week on jk3files.com that have nothing to do with MBII. The majority of activity is centered, as it has been, around small communities picking up every new player they can from $10 sales at Walmart or whatever.
MBII requires a little knowledge of modding and all sorts of things that those players can't be bothered to learn. (This is, of course, though, why all the server settings are crappy on all the servers, because all the old admins and vets that had any sort of net-code experience have left for the most part). JA+ is pretty easy to get people to use by comparison, because servers still show up on lists without the mod.