The BMW car forum is good, bimmerforums.com. Pelicanpart forum is good. BMW/Porsche GrassrootMotorsports is good. General racing, falls back to bmw/porsche/corvette/mazda Miata.net is fantastic. Corvette forums are great, but I can't recall them now. Subaru Forum is fantastic, humour though is needed. NASIOC.com priuschat is great, though it goes quite different from above forums. Tesla forums are good, but I can't recall any off the top of my hand. And then landcruiser ones, wrangler/jeep ones, etc.
The more less hobby a car is, the decrease in quality in forum posts, not that a corolla is a bad car per se, or even a camry/accord. It's just, different folks for different hobbies.
Spend a week on there, and you'll learn the lingo (it's universal throughout cars, especially per car generation/period, 70's/80's/90's,etc)
Then you also have other motorsports too, motorcycles and even planes, which share the same sentiment. Pilot chat/bicker is very similar. ;)