http://www.pnwbemani.net/There's a Bemani (Rhythm Games) community site that's been up and running for a while. I tend to schedule DDR or other bemani-related events and only announce them there, so I encourage others to join the site, especially people looking to have fun playing games with fellow enthusiasts, instead of being antisocial in your basement.
I figure it's only fair to link there from here, since people talk about Kumoricon and (more often) Sakuracon there pretty often.
A note to the moderators/admin:
I don't think this counts as advertising, because the site is purely a community forum which doesn't even have ads. If this is an issue, lock the topic, I guess.