Better (and cheaper) than the traditional Sunday drive...
Madison offers a full size zoo. It has the works, lions, tigers, bears, flamingos, monkeys, penguins and etc. The park is well-maintained and a tolerable stroll (as opposed to the foot numbing extended walks of the Milwaukee County Zoo) without damaging your wallet.
The only difficulty is getting (and parking near) there. Nearby roads have been pounded with construction for over a year. Your car will feel the effects of half-finished roads and poor detours. Parking is another problem, but since it is free and available to those that come early (and make it through the construction), that complaint lacks validity.
Visit the wonderful park, eat at their value-conscious (and adequate) concessions and stop over at the gift shop on your way out ... you will leave Henry Vilas Zoo as if you left the Fountain of Youth.