I simply do not have the floor space to knock down plywood either on the tablesaw or on sawhorses. I needed the ability to cut plywood while standing on edge. I could not justify the $$$ for a retail panel saw, so I came up with a solution that lets me accurately rip and crosscut full sheets while they stand. What started as a harbor freight moving dolly (four wheels for $16!) quickly evolved into a functional cart (or giant skateboard) and then into a simple plywood cart with two sides; one for plywood storage and one for plywood cutting. The sides are sloped 10 degrees to allow plywood to rest and I kept the height pretty low at around 30" to give some space for storage in between the two sides. The rope you see is connected to a bungee at one end to snuggly hold the stored plywood.;
Crosscutting plywood is dead-simple and fast. The inspiration for the crosscut sled was your normal, every day drywall square; it rests on the plywood itself and guides the circular saw. Almost made a major mistake when I realized the saw in the sled would cut through the tee crossbar itself. Luckily I backed that up with another piece of plywood first. If I had it to do again, I would use thinner plywood -- the tee weights in at about 15lbs! I just line my cut line up with the kerf through the sight-hole and run the saw from top to bottom. Perfect cut -- the sled acts as a zero-clearance and minimizes tearout.
Ripping plywood is super-easy. I made two small tees that represent the width of the sled to the outside of the saw blade. I clamp those to my line and slide a long straightedge underneath, and clap that. I have no idea where it came from, but I had an old 8+' aluminum tee laying around that worked wonders. I imagine a straight piece of plywood would work too. Full sheet to cut in about 30 seconds. Basically this is the exact same procedure for ripping when on sawhorses, just using gravity to hold the saw to the guide.
The hardest part of this whole build was mounting the circular saw to the 3/4" mounting plate. My saw wouldn't do a full plunge cut so I used a 6" dado blade to get it started. The next hardest was probably cutting the 10 degree angles, but you can get real close (from a slope chart) by using 5" per 30" as the slope.
Total out-of-pocket cost for me for this cart was about $50 - $16 for the wheels, $18 for a half-sheet of plywood and about $15 for 2x4s. The rest was scrap I had laying around. I suppose if you were to start from zero, the lumber in this build would be less than $100 for the 1x4 and odds and ends. The circular saw I rescued from an auction for $3.
tip: if you use dimension lumber in the spacer in the tee, then the sled (which is thinner plywood) will slide nicely under the stops.
tip: for measuring the rip offset on the tees, try to keep the "heavy" part of the saw down. This avoids tipping for thin rips. Also, it helps to clamp one end once sawn to avoid the kerf closing from gravity.