This was my first project as I jumped into woodworking.  I needed a easy-to-build but sturdy workbench.  Two sheets of MDF make the top and 4"x4" posts make the legs.  The stretchers and rails are standard 2"x4" and have groove routed in them.  Inside each grooves sits a threaded rod which also passes through the legs.  The threaded rods are then cinched tight on the outside of each leg, resulting in great stability.