Bike stand built from 1x4, 2x4 and 2x6 construction lumber designed to fit a Workmate. Cost - since I had scrap lumber, about a dollar for a couple of carriage bolts and wing nuts. Took longer to document in SketchUp than to build, but it was good practice for using SketchUp. One advantage of this design is it can be broken down and hung from a nail in the garage for storage.

Don't have a Workmate. Check out http://bluecollarmtb.com/2005/03/02/bike-repair-stand-blue-collar-style/

Step 1: Arms

Cut two pieces of 1x4 24 inches long for the arms.
One arm has two 3/8 dia holes drilled in it 6 1/4 inches from the end and 3/4 inches from the top and bottom.
Use these holes as a guide to drill the upright and other arm after everything is assembled.
Cut two pieces of 2x4 3 1/2 inches long for the spacer blocks.
Screw the arms to the spacer blocks so there's a gap in the arm assembly for the upright to fit through snugly.

Step 2: Upright

Cut a 2x6 30 inches long for the upright.
Cut two pieces of 2x4 15 inches long for the support blocks.
Attached the support blocks to the upright 2 inches from the bottom of the upright.

Note: As an alternative, attach the support blocks flush with the bottom of the upright, then the stand could be clamped to the edge of a workbench

Step 3: Final Assembly

Slide the arms over the upright and use the holes you drilled in the one arm as a guide to drill holes through the upright and the other arm.
Drill a series of evenly spaced holes down the upright so the height of the arms can be adjusted.
Attach the arms to the upright using two 4 inch long 3/8" carriage bolts, washers and wingnuts.
Clamp the whole thing in the Workmate as shown. You can also clamp the back of the support blocks down to the Workmate table for extra support.

Step 4: Holding Bike

The bike can be held loosely up off the ground by the slipping the seat post or seat tube between the open ends of the arms.

If the bike needs to be held rigidly, put a C-clamp over the open end of the arms and tighten to clamp the seat post/seat tube between the arms.