My Pyramid Drill
 

The Pyramid Drill works this way...

1 Pyramid:

10 Swings with club shaft
10 Swings with club
10 Swings with weighted club (I use the Momentus)
10 Swings with club
10 Swings with club shaft

I personally do 2 Pyramids in each session. Done correctly, this drill will build up your golf specific muscles as well as give you a rather taxing aerobic workout.