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:
http://www.woodshopdude.com/

I plan on buying the plans unless someone here has a link to a better
design