Welcome to my first instructable.
I am entering this in the Shelf Contest, so please vote for me if you feel it's worthy!
Each shelf consists of two parts: The frame, which get attached to the wall, and the sleeve, which slides over the frame.
I made the sleeves 24" wide by 16" deep at the top, and the frames are 19.5" wide by 13" deep. This turned out to be deeper than I needed, and I may reduce the depth in the future is they start to sag.
Each frame is connected to the wall with two drywall anchors using 1/4" x 3" bolts, as well as a 1/4" lag screw into the stud. I wouldn't try hanging off them, but they're strong enough to support any device I'm going to put on them.
Finally, the frames and sleeves are designed so the the cables and power cords for each component can disappear into the wall cavity through a hole drilled into the drywall. I will fish all the signal cables to the access panel above the middle shelf and then through the stud to another access panel behind the TV. All the power cords will run through the wall cavity, down to the power outlet above the bottom shelf.
Step 1: Design and Assembly
I don't have pictures of every step of construction, but I can tell you that for the frame,I ripped 2 x 4's so that I had two 1.5" x 1.5" pieces.
NOTE: I started by designing the frame and built the shelf around it. In hindsight, I should have started by designing the shelf and built the frame to support it.
The frame was assembled using brad nails and screws and glue.
The sleeve was assembled using brad nails and glue. I filled the nail holes, sanded using increasing grits, and then primed and painted.
Step 2: Layout and Installation
I spaced out the shelves evenly. The top of the top shelf is in line with the top of the TV, while the top of the bottom shelf is 1/2" below the electrical outlet.
NOTE: The top of the shelf is above the top of the frame, so I first marked where I wanted the top of the shelf and then, using a level, drew a line where the top of the frame would go (in my case 3/8" below). I also marked out where the left corner of the frame would go in relation to that line and copied it down to the other lines using my level so all the shelves would be aligned.
Once I had the locations of the shelves marked, I drilled a 1-3/4" hole for each shelf's cable run. I used a 1-3/4" forstner bit, they make a lot of dust, but they also make a very clean hole, which is good since the will be somewhat visible from above.
I held up each shelf where it was to go and used a nail to mark the location of the toggles bolts. I installed the toggle bolt sleeves in the drywall, and then hung the frame. For added strength, I screwed a 1/4" lag screw into the stud.
Once all the frames were in, I added the plastic access panel and slid the sleeves over the frames.
All done, now it's time to place the components on the shelves and clean up.