Weider X-Factor ST
Premise: The program cycles through a series of six bodyweight-only exercises back to back (such as burpees, punches, and jabs) before a brief rest, then repeats the high pace with six additional exercises.
Pros: The only equipment you need is your own bodyweight and the pair of rotating push-up stands that come with it.
Problems: Depending on how much you weigh at the start, the eight-week program may not allow you to build as much muscle (if you're lighter) or could be too difficult (if you're heavier).
Perfect for: Anyone looking to get buff on a tight budget. [$39.99; weiderfitness.com]