Check on USAHockey and you can find all of the ones affiliated with USAHockey. I know one that is not on par with the GLHL but has some pretty good talent in it including Hockey Hall of Famer Steve Shutt, the Northwest Florida Hockey League (NFHL). NFHL Website
Here is some info on the Great Lakes Hockey League;
The league origin as explained to me, started sometime in the early 1900's as a Wisconsin only league. In the late 1930's the 2 Michigan (UP) teams joined the league. It is now Amateur USA Hockey Adult full check league. The league is very well organized and competitive. Some of the teams have been under the same management for over 30 years. It is a great place to play after juniors, college or semi-pro leagues for players that want to play in a competitive enviorment. The league championship team get their names engraved on the traveling Kohlman Cup.
For the first time in the history of the league a new team from Illinois has been admitted in the league.
I hope that clears up some of your questions.
Vernon Hills Capitals, I see. I think it makes some sense for the the GLHL to expand down into the Chicago area. I like the GLHL as a league and wish there were more leagues like it around the country. In some regards, the GLHL is close to semi-pro hockey (regional checking hockey league for which there are tryouts, the teams actually stick around a while, etc.).
I would certainly expect the Vernon Hills team to field a good roster, because there are plenty of talented players around the Chicago area who have junior, college, and pro hockey experience. That might be the risk some of the Wisconsin teams face in expanding the league to the Chicago area is that there are a lot of good players in that area to pick from.
If you're from the Chicago area, especially north suburban Chicago, and were considering trying out for an MAHL team, consider trying out for this team instead. You'll play competitive checking hockey and be able to hold down a job that actually pays, too.