I belong to the New Jersey Triumph Association. I used to go to the monthly meetings since they are held at a pretty good local watering hole which is only about 20 minutes from me. Was a nice excuse to get the car out on a weeknight, especially in the better weather. Haven't been going for close to a year now, mostly due to bad timing every month and other priorities.
The meetings are usually pretty good, people sit around and trade stories over a few pints, that kind of thing. The club officers also would try to line up a guest speaker or some activity every month. Once we had a guy in from a local shop that serviced classic Brit, Italian, German cars (they did alot of Ferraris, classic and modern). He gave a talk on tuning carbs, timing, basic good tune-up knowledge. Then we had a guy in that worked for Lucas for 30 years, he gave a talk on electrical systems and common problems (we were gentle on him, not to much heckling or price of darkness jokes, although he seemed to have heard them all anyway). The club also arranges some nice activities. They set up a bunch of shows every season, including helping the local MG club in setting up with Moss for the Fallfest show in Dover NJ. We also do a fall foliage drive around the time the leaves change, an ice cream run, and a show in Princeton at the Triumph Brew pub, amongst other things. My only complaint is the monthly news letter, it's taken a real turn for the worst. It used to be filled with little how to articles, classified ads, stories of past glory, etc.. Now it's basically just a piece of paper with the club officers phone numbers, the season activity schedule, and not much else. This club has about 200 members if I remember correctly. Our club president is also the owner of a local classic Brit car shop, so he often hosts open garage days, usually on a Saturday, where club members can come down and put their cars on the lift and his mechanics will help you go through and sort out problems. Overall I guess thats one of the best parts of being in a club, there's a wealth of technical knowledge there that you can tap into, plus the comaraderie is nice to.
I used to belong to the central jersey mustang club, back when i had the stangs. I'll probably join that again when I get the new one. Things there tended to focus more on performance, they would all coordinate for track days at the local drag strips so club members could meet up and run against each other. This was a fun club also but a completely different atmosphere than the Triumph club.