That all depends on what you consider 'good'.
Massassians tend to stick to addon levels and mods, but actually playing them is a rarity (a few games a week that aren't private). If you're only looking to play a few times a week and are a big fan of mods and addon levels (good and not-so-good), then #massgames is your place.
The Internet Gaming Zone, also known as a wretched hive of scum a villany, is by far the largest active JK community (even to this day). There are alot of *******s there, but occasionally you'll run into some nice people that don't even have to use cheats to win a game. They play both mods and addon levels on the Zone, but they actually play some of the original levels as well, which is unique these days. The biggest upside to the Zone is that you can get a game at just about anytime.
The other communities such as Gamespy Arcade and Qtracker are practically dead, although a few poor souls still play there (even myself on occasion, Qtracker is a great program when the master server is working).
The best thing to to is to build a group of friends online and just play IP games over AIM/GAIM or what have you. I've done this with my clan and some friends and we're able to get a game of CTF (which is what are group is for) just about any day of the week.
Good luck!
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