Ok, I've had really good success with extra workouts lately, as far as improving fitness, strength and body composition. It is important to increase your nutrient intake when doing extra workouts. It is also important to mix up your extra workouts to avoid overtraining.
Here are some good ones I've been doing lately:
50 bodyweight squats, 50 cossacks (that's what pavel calls it anyhow), 50 lunges with each leg.
run on the step mill at level 12 for two minutes, walk around for about six minutes, then run on the step mill again like before.
20 pushups, 5 one arm pushups with each arm.
Front, Side and Back leg kicks with 10lb ankleweights, to fatigue. For the back leg kick, hold on to a chair or something and bend over some what, think of it like a one legged reverse hyper. It's really good!
20 hindu push ups, rest then do as many row push ups with 20lbs as you can.
Run to the top of a hill approximately one block in length. Walk down the hill at a relaxed pace. Repeat three or four times.
Dynamic tension exercises, sort of like pilates on roids I guess. I do lots of chest, back and shoulder movements where I move the arm through a full range of motion, and I try to maximally contract the agonistic and antagonistic muscles. If these aren't hard for you, you're not trying hard enough. I also practice rolling the shoulders back as far as possible and holding them tight by squeezing the back muscles as hard as possible to improve my setup on the bench.
Additionally, if you have access to a pool, try doing flutter kicks in chest deep water as fast as you can. Just kick one leg up high, then bring it down quickly, and as you are bringing it down kick the other one up at the same time. This works the hell out of your hams, quads and hip flexors. Better for recovery than dragging a sled I think. You can also wave your arms back and forth under the water in a fly motion rapidly, this is a good way to condition the upper body. I like to swim as well, sometimes I'll do 6 lap swim sprint intervals.
Also, benchers should put extra work into shoulder flexibility.