If you wanted to go very simple, just start your own forum. They are free, easy to set up, and you can section it by area. It allows people to sign in and have accounts, and some are already built in to have supporters. That would be easy and nothing fancy. It would just be a forum for only the garage meet ups.
I wonder if my work would let me do something like this... but instead of going around to everyones garage, you could get your car into the shop and everyone could work together. Maybe have a very reduced shop fee... could be a working BBQ. *mental cogs turning* hmmm