The RV.net B12 Rally is open for registration for next May in North Carolina. Details are here:
http://www.b-rally.org/
Two conditions you should know in advance. First, you have to have a true Class B built from a van. That excludes anything built on a cutaway chassis. Secondly, you have to have a registered screen name on RV.net. I'm not sure why of that second but the B1 Rally was organized on RV.net and tradition continues. Most of us here already do.
It has been a great rally. You meet lots of people with many different kinds of Class Bs as opposed to manufacturer specific rallies. There is a cost of $30 per person plus you pay your own campground fees but all food and entertainment is provided on the grounds. I've attended several starting with B4 that was in North Carolina. Last year it was in southern Indiana.
There are 36 sites available and then that's it. A waiting list of a half dozen usually makes it as people do drop out after registering. Last I checked it was 24 Class Bs filled after just two days open.
I'd like to meet some regulars from here.