One thing that works good for me is circuit training, or interval training.
I set the timer on my watch for 3 minutes (countdown-repeat cycle). I cycle through different exercises, about 10 or 12 stations in total. I usually go through fast run on treadmill, pushups/situps, jump rope, weights, and throw a stretching block in there somewhere for some rest!
Makes the workout go fast, and seems to be a well-rounded one as well.