The big blue box store is practically giving away the Jawhorse miter saw attachment for around $20. I bought one even though I don't have a Jawhorse because it came with some rollers that clamp to 2by lumber and some nifty right angle clamps for 2by lumber.
I started googling to see if there are any new ways to build a sawhorse since one of our own came up with those three legged things and came across this design: