Jon Pope's eponymous design firm helps companies such as John Deere, Timberjack, and Gehl create cutting-edge cabs and exteriors for a whole range of construction equipment. Their renderings, though, are the true gem.
Among the more standard pieces of super duty construction equipment, Pope Design also has some really great (and out-there) concepts, like this scissoring Straddle Carrier for shipping containers.
There's also this walking crane...
...and a portable wind turbine.
Pope has posted a handful of hand drawings on his company site, Pope Design
One more for good measure: