Lunge University is a workout popularized by the man himself: Mr. Cory Gregory. It seems like the best workouts are the simplest and lunge university is no different. All you have to do in order to accomplish this workout is strap on your favorite music, inspirational/motivational pod cast and then start doing walking lunges. You'll want to shot for around 1/4 mile of lunges (I typically will do 400 steps when I do them inside).
Once that gets too easy, get yourself a weighted vest or do 1/2 mile of walking lunges.