In recent years, our friends over at the Sega8bit.com Forum have been organising meetups in Manchester (UK), where people play (mostly) Master System games, trade, chat and generally have a bit of retro fun. There's also a competition - with a real trophy - to add a frisson of additional excitement to the proceedings. Oh, and it's in a pub, so there's food and drinks if you like those sorts of things.
Many of the regulars there are also regulars here, and I've been a few times myself (I'm even the current trophy holder, somehow). If you can make it to Manchester for a Saturday afternoon this August 10th, you are welcome to join in.
(There's no sport on that Saturday, by the way. Except maybe some Olympic Gold, California Games, Pro Wrestling, etc...)
The best place to discuss it is over at the official thread at the Sega8bit.com Forum, where you can post to say you're coming. This year I'm organising the competition - and excluding the games I'm good at - so there's some discussion to do for that, too.