^^ this. if you're pressed for time, crossfit is amazing (well it's amazing anyway).

my cf gym is full of professional people-- doctors, lawyers, and engineers and by looking at them you'd think they were gym rats.

I second this one. You're really wasting your time if you're there for more than 45 minutes. Means you're resting too much between exercises. Quality over quantity when it comes to gym time.

For example, do 5 pullups, 10 pushups, 15 burpees, and 20 jumping jacks. Repeat ten times with little rest between rounds. Then jump rope a 100 times.

Should take you no more than twenty minutes. It's hard to get up from that one though.