This is what I do..

Get a Black N Decker Work Mate

next go the Habitat to Humanity Re-Store, Find one near you.. Seattle store might be the best bet.
http://www.habitat.org/cd/env/restor....aspx?place=72

Look around there for a kitchen island counter top.. I got a 5'x3' for $15
If you cant find that get a flat solid core door.
Screw a 2x4 to the bottom and clamp it in the workmate..

Easy cheep and portable.