This was hacked together quickly to solve a problem. I hadn't used Meteor before. The UI is extremely basic and only barely works. Use at your own risk.
Imagine you run an event and want the participants to form groups of three for an activity. The common options are either slow ("Please form groups!") or suboptimal (by fiat or by counting).
This app automates the group forming process while taking people's preferences into account. It works best for recurring events where participants can register with the app in advance.
The idea is that people will figure out whom they work well with and then update their (private) matching settings. From then on they're more likely to be in productive groups but not working with the same people every time either.