I like to get in one good treadmill interval session per week.
Research has shown that interval training has a significant advantage over traditional steady state cardio as it relates to building lean muscle, fat loss, and post-exercise elevated metabolism.
Combine it with some core work and you've got a nice workout that will get you ready to take on the day.
I've been running intervals using the 60:120 of Montreal soundtrack from WorkoutMuse. Great music and a great workout! What could be better?