This is how I get my equipment around at a commercial shoot.
This is the RocknRoller R16 cart. They are marketed mostly toward musicians and audio techs but they are great for photographers. They come in various sizes and they adjust to fit the load as needed. This model can carry 600 lbs of equipment and at times I feel that I have pushed the limit.
The cart folds flat for storage and during transport. It is very well made with steel and the wheels are large which makes it easy to push through grass and over sand. After loosing two bolts on the bottom the base of the cart extends to accommodate different amounts of equipment. Some carts even have attachments available so that a work shelf or even a laptop table can be added.
