Digging this Ikeahack by RainyDayMagazine. Ikea's Capita brace, stock shot above, is meant for adding an elevated, off-set ledge to a table. RDM's Wan & Carolyn took four of them, mounted them outwards on a shop cart and connected a tabletop, with neat results:
One ergonomic issue they're candid about is that the table is not ideal for dining, as leg space underneath the top is limited. This seems easy to rectify though, as you can add a wider tabletop or use a narrower shop cart.
I think this would be a great solution for a workbench, with the braces turned inwards; then you could have your work surface on top holding an object you're building or repairing, and all of your tools laid within easy reach on the secondary surface.