It's a tricky question. There is a LUG in Ireland which I only found out about a month or so ago and they do meet monthly. I'm a member of their website and keep an eye on it. However, they are centred largely around Dublin and I'm on the west coast so to get to a meeting is near impossible being just shy of 200km away.
So I guess, yes I'm a member, no I don't really support them at this time.
I do participate online on other sites and have posted here a few times as well and often post on the likes of BrickSet and have done a few small reviews. If I had more time, I would probably participate more but I have 2 young kids, pre-school, so I'm kept busy all the time and barely get much time building stuff.