How about a 6 week routine. I have done this in the past and found it challenging.
Pick 8-10 exercises(covering all body areas -- legs, arms, chest and back.)
Determine your 1 RM max for each exercise( the max amount of weight you can lift properly 1 time)
For 2 weeks perform 30 reps(without resting if possible) of each exercise at 50% of your 1 RM max. ( ie your 1 RM is 100 your workout weight is 50 )
At weeks 3-4. Do 40 reps at 40%
For weeks 5-6. Do 50 reps at 30%
Perform every other day with cardio and abdominals mixed in on non lifting days.