Regular doors are boring. This is a pocket door based off of barn door hardware. Due to the capacity of the hardware, its possible to build shelves into the design. There are some awesome hidden doors that when trimmed out are impossible to detect.... this isn't one of them. It's in a workshop in an out building, so... fine woodworking would be a little out of place.... The secret here is that most people will see the shelf and not a door.
I didn't plan on an instructable, so I didn't always take perfect photos during construction, but I will try to explain the best I can. I built what fits for my application, for that reason, I omitted exact measurements. The paneling was used due to it's light weight for the door, and I had a boatload to use up and can be seen in my Landspeeder instructable.

The door opening ended up being 81" tall by 56" wide.
The shelf depth is 11.5", and the capacity of the door 450lbs... which should be more than enough for most projects I imagine..

since this was originally posted, I also incorporated a wooden lock into the design.

Step 1: Figure Out What You Have to Work With

With the sweep area considered, the door takes up twice the space as the opening that you'll want at the end so make certain that you assess the project carefully before you start.
This is the proof of concept photo.
The hardware used was National Hardware brand purchased from Tractor supply. the trucks and the rail itself came to around 100.

Step 2: Header

The area I had to work with was perfectly suited for this this design or vice versa, A thick beam needs to span the entire opening to support the track. The placement of the beam to the structure behind will ultimately determine the depth of the door assy. If the track is mounted to a wall or directly adjacent to the passageway, there will be no depth to work with. This will result in a regular panel type door (of which there are better suited instructables most likely.) The "show" side is easy to build around.

Step 3: Rolling Test

In order to balance the sliding unit, the hanging hardware needs to be centered in the sliding sub assy. To do this, I built an inverted T the length of my intended door that the rest of the unit could be built on.
Every step was proofed out as I didn't want to mis calculate.

Step 4: Build Door

baby steps, lots of putting on door/taking off to test/build.

Step 5: The Working Parts Work

Here the business end is pretty much shored up... it all works the way it should. The shelf door is backed with paneling,

Step 6: Making It "pretty"

With the door in place and working, you can now build a wall offset the exact distance that you need for your design. To do this I just made spacers above the track to the header.
Instead of tying to the concrete, for the bottom, I made a substrate that tied back to the stair stringer to keep the wall from swinging out or being pushed in. Ultimately this is totally reversible if need be.

Step 7: You Get the Idea...

A few design features I toyed around with are a "floating" trim piece at the bottom to hide the gap at the floor. this would be simple with some slots allowing the trim to slide up and down as needed to meet the floor. This is an uneven garage floor, so Its about as good as I need it. Also, since the bottom of the door is a large cavity, its feasible to tie a rail system that mates to the floor behind the wall cavity. This would tie the door at the top and bottom removing any fore aft sway.
Be sure to attach a handle on the back side of the door so you can open it from behind. From the front, a little shove on the side moves it with no problem.
a lock could easily be incorporated into this or maybe some secret latch in the future.
http://youtu.be/AbRtI43iuGw
the door is not usually this loud, it was an EXTREMELY cold day when the video was taken.