The premise of MathsJam is similar, although slightly more informal, to a teachmeet, of which I am a well-known lover. The events take place in pubs up and down the country on the second to last Tuesday every month with the idea being that you can bring along a puzzle or game or anything maths related if you want to (you don't have to bring anything) and sit and play/chat/drink etc. The great thing about them all happening simultaneously up and down the country is that different MathsJams can set challenges for everyone via their twitter account @MathJam and it makes it easier for different groups to collaborate/send messages/challenge, or whatever you want to be achieved, with the help of mobile technology.
Last night there were six of us, well up on the three from last time (the first one in Northampton so doing well number wise!) and we played with various things: Pass the Pigs (plastic pig shapes with the ability to land 6 different ways like dice); Sicherman dice; a couple of iPad games - SET and Torus Games; how to make an Enigma machine out of a pringles tube; 3-player chess boards; the game 24; and those annoying metal puzzles that you have to try and get apart and back together again. There was no order or agenda to things; the puzzles and games were just shared and you dipped in and out of what you wanted and when.
Our messy maths. Picture courtesy of @rathematician
I'd definitely recommend going along to one if there's one near you; they're really not as scary as they sound. There's a map to find out current MathsJams that take place or you can request to set up your own if there's not one nearby:
View MathsJams current and potential in a larger map