The thing that makes these questions hard to answer, is that MMA doesn't have leagues. The number of known fighters depends on the viewers' interest in the sport. Casual fans will most likely just know fighters that are fighting in the UFC, or have at some point.
Besides UFC, you should check out WEC, Dream, K-1, Strikeforce, King of the Cage, Bellator Fighting Championships, and whatever organizations you can find depending on your interest.
If you want to learn some history, watch the old Pride FC fights. Tons of good material there, and their dvds are dirt cheap.
The amount of events a month is always fluctuating. Tonight's UFC event is the 3rd in 2 weeks. That isn't common though. The UFC and WEC are definitely the most driving forces of MMA. Strikeforce and Dream are coming up though, and are starting to get better fights.
UFC.com has a fantasy section. This forum has a vbookie which is fun for betting points that you gain for posting, polls, etc.
Watching old UFC footage and Pride FC footage will give you a deeper perspective on today's MMA world. I suggest doing that.
Last edited by elardo; 03-31-2010 at 02:20 PM.