I'm probably missing something obvious here but where do you go to see a list of past champions in the league? Also I see where you can select to see regular and preseason standings, how about previous season post season results?

On the league page above the schedule in the right column, click "View All." You will be presented with the full schedule for the current season. There is a drop-down to each season's preseason, regular season, and playoffs, as well as an option for all league championships.