Weekly awards, given out publicly
A single named award each week, announced in the same place every time, is the cheapest engagement tool there is. It gives people who are out of contention something to win and something to lose.
The trick is that at least one award has to be bad. An award for the highest score is a lap of honour for whoever is already winning; an award for the most points left on the bench is a running joke anybody can enter and nobody wants.
Name them after people in your league rather than after the stat. The Marcus Rule outlives Most Bench Points by about three seasons.
By hand: Ten minutes a week if you pull the numbers by hand. The failure mode is missing a week: skip one and nobody expects it again.
In CommishCast: Five are computed and announced every week automatically — Top Score, Bench Disaster, Waiver Wire Hero, Stolen Win and Bottom of the Barrel. You can add one of your own from a list of tracked stats, including most transactions, longest losing streak and most points in a loss, and name it whatever you like.
Power rankings that are not the standings
Standings reward luck. A 5-1 team that scored the fourth-most points in the league is not the best team, and everybody knows it without having a way to say so that sticks.
Rankings that account for points scored, points against and schedule give the league an argument every week, and arguments are engagement. Publish them with one line of reasoning per move.
Being ranked below your record is far more motivating than being ranked at it.
By hand: Twenty minutes weekly, and it needs a consistent method or it reads as favouritism.
In CommishCast: Rankings are part of every weekly episode, with the reasoning said out loud rather than left as a number in a table.
Rivalry weeks, declared in advance
Pick the four matchups with genuine history and name them in the preseason. A week that has been on the calendar since August is one people plan around.
The pairings do not need to be close on paper. Two people who have argued for years make a better rivalry than two good teams who have never spoken.
By hand: An hour once, at the start of the season. Nothing weekly.