My league used to use an open source software called OFFL to manage the league, do the scoring, etc.
It was a great solution. But last year NFL.com changed the way it displayed the live scores - which broke OFFL. I'm not certain if they ever got it working again.
Luckily for my league, we had already moved to ESPN.com's free leagues. I was afraid something like the NFL.com change might happen, and OFFL had been great, but also a bit of work to maintain.
Both of these solutions have worked well enough for us. But one area where neither really rocked was in the scheduling department. OFFL had no built in scheduler, and ESPN's is pretty weak.
Footballguys.com has a great FREE scheduler - it lets you specify all sorts of parameters (divisions, number of times each division plays, etc) and barfs out a schedule for you to enter into another system. Thanks!