A pretty easy workbench made out of some 2x6's, a piece of 3/4" plywood, and a piece of 3/8" particle board. It's something that my Dad designed that we put together.
Step 1: Parts
As for the size of the workbench, the table top dimensions and table height is completely arbitrary. It can be pretty much any size you want (I'd guess that the table top should be no bigger than a 4X8 sheet of plywood). The table top size for this Instructable will be 6.5 ft X 2.5 ft. For that, here's what I needed:
2X6 Wood Boards: 6' cross beams x2
2' leg braces (dog eared) x6
30" legs x6
39 Feet total
3/4" Plywood: 6.5' X 2.5' tabletop bottom
3/8" Particle Board: 6.5' X 2.5' tabletop top
*note: The table top dimensions are a half foot longer than the cross beams and leg braces. I picked these dimensions because I wanted to have about 3 inches of overhang so that I could have a place for C-Clamps, etc.
2.5" deck screws (or something close that length than has a flat head): x33
4.5" bolts: I think i used a 3/8" diameter bolt with nuts and washers x24
Step 2: Assemble Legs
Align a leg with a leg brace. The top of the leg should be flush with the top of the leg brace. The leg brace should extend 2 inches past leg. Drill 2 pilot holes and secure with 2 bolts. Repeat at the bottom of the leg. Secure another leg at the other end of the 2 leg braces. Complete this leg assembly 3 times.