Oilfield Truck with trailer.

Features:

A.Dual steering 

B.Working crane. Basically is the same design as from the technic set 8431
  just modified a little.

C.As with all of the tractors that I build, working drive shaft that runs
  off of the front drive axle

D.Air Ride individual suspension (sort of)(using sponges for this. They work 
 real well) on the drive axles as well as the trailer.

E.As you might be aware, there is a piece of the drive train called a yoak
  (spelling?). Since Lego doesn't make one(!)... maybe someday???, I needed
  to improvise. The drive shaft still has the ability to slide back and forth
 like you would have on a real rig, it's just doing it in a different way.
 Check out the folder "driveshaft" and you should be able to get a better 
  idea of how this is done.Basically, you have a axle going through a 1x2 
 or 1x4 teck. brick while leaving room for it to slide back and forth but 
 not enough that it will slip out. 

F.Retractable feet for stability when the crane is working. 

G.Working feet for the trailer. I use a gear box with a worm gear for this.
  The feet will hold the weight of 1.5 city telephone books(!) without
  collasping or breaking.

H.Working fifth wheel. Fifth wheel tilts forward and backwards.Check out 
  any of the other folders that have a tractor or trailer with a fifth 
  wheel contraption on it to see how it works.