"No abusing the rules" probably only works if people can coordinate successfully on "the spirit of the rules".
I think one direction to explore is to have a games master picking sets that are easy to define (at least roughly), but hard to enumerate. Things like "locations in New York", "subsets of the integers", "nonempty finite subsets of the irrational numbers", "letters in non-Roman alphabets", "man-made satellites currently orbiting Earth", "models of jet plane", "movies released in the 1980s". Then teams compete to coordinate on the same sets, instead of presenting sets to each other.
You need the GM because problems can be arbitrarily complicated ("{locations in NY} X {subsets of the integers} X ..."). I'm not sure how ambiguous-membership would be handled. My first thought was that if everybody in the team agrees that something is in the set, it counts; but you need to be able to disqualify unambiguously-wrong answers, or everybody just agrees to answer "the information desk in Grand Central Station at noon" regardless of the question. I suspect you can just allow the GM to veto such answers on discretion.
A month ago, a new type of thread was proposed: a monthly page for meetup reports. The idea is that meetup attendees, or organizers, who wanted to share information about how the meetup went could do so in the comments of this thread. This is so information is dispersed, but without the need for anyone, and/or everyone, to dedicate their own thread to the report. The idea worked for January, and nobody had objections. So, we'll do this every month.
If you had an interesting Less Wrong meetup recently, but don't have the time to write up a big report to post to Discussion, feel free to write a comment here. Even if it's just a couple lines about what you did and how people felt about it, it might encourage some people to attend meetups or start meetups in their area.
If you have the time, you can also describe what types of exercises you did, what worked and what didn't. This could help inspire meetups to try new things and improve themselves in various ways.
If you're inspired by what's posted below and want to organize a meetup, check out this page for some resources to get started! You can also check FrankAdamek's weekly post on meetups for the week