There are a number of various forms of fantasy baseball out there. Obviously you have H2H, Roto & Points based leagues. But I'm interested in your variations to these themes. What variation have you dreamed up? Is it any good? I'll get things started with mine:
I call it a "Pick 3 Teams" league. The premise is pretty much what the name suggests. Every manager gets to pick 3 actual MLB teams. Then they get access to every player on that MLB team for their own use during the fantasy season. You can use this to play any of the forms of fantasy baseball (H2H, Roto or Points). I personally am using a Roto league. I have recently added one new rule to my leagues. You are now allowed to make ONE trade only for the whole season. That trade must be a one-for-one player swap. This allows for owners to make a slight modification on their team.
As for deciding who gets what MLB teams, there are two ways of deciding. Of course you can have a draft. Or you can seperate all thirty MLB teams into 3 groups with 10 teams each. The top 10 teams in group #1. The middle tier teams in group #2. The bottom tier teams in group #3. Then every manager, when they join your league, is allowed to pick one team from each category. This way every team has a solid, mediocre and under-achieveing group on their team.
This has proven to be a nice variation on fantasy sports. I actually do this on basketball as well.
NOTE: As a side point, I have a "Pick 3 Teams league where I still need 5 more managers. If your interested, send me a PM.