Cinema5d has published a cool little (ok, it isn't little, it is darn big! 26 pages big!) review of a bunch of HDSLR rigs. This is something you've really got to take time to wade thru if you're interested in rigs.
This is just a small snippet from the introduction….
“The sum of the parts that we add to the new DSLR cameras is the thing we call a â€œrigâ€. Itâ€™s what extends your cameraâ€™s body to make it ergonomic for cinema style shooting. The way it is set up depends on what youâ€™re shooting.
Usually the more sophisticated camera configurations are handheld rigs. Not only do they have to conveniently and safely hold together basic parts like for example a matte box, follow focus, monitor and/or microphone but at the same time balance all weight comfortably on your shoulder so you can create good camera motion and be able to work fast and long hours.”
(Photo credit: snap from the cinema5d site)