Upper and Lower Body Days
This timesaving tip may not be suitable for everyone. But if you're having trouble getting motivated to weight-train - or if you need shorter training sessions - this strategy may be worth a try.
Instead of a "complete" weight-training workout that exercises all the body's major muscle groups, alternate your routine so that on one day you train only the upper-body muscles (arms, shoulders, chest, upper back) and on the next day you train just the lower-body muscle groups (abdomen, backside, legs). With this schedule, all the muscles have the day's recovery time they need.
The upside: with each session, you could be finished in 15 minutes or less.
The catch: although you'll have shorter training sessions, you'll need MORE of them. For example, you'd need four short workouts instead of two full-body workouts. But if getting in and out of the weight room quickly is a plus, this schedule could be right for you.