Well, I'll throw out the
WBH. It is a fictional promotion/relegation league with 4 levels of leagues. We are in our 6th season and we have 9 leagues and 72 total teams. We generally expand every 2 seasons, so there will probably be 2 more leagues opening up after next season (Puerto Rico and Panama started play this current season).
Great league, great group of owners, and an amazing commissioner.