We needed a small wood storage cart on wheels to safely store small cut sheets of plywood and masonite, and with a second side to contain cut dimensional lumber.  I took my design from Woodworking for Mere Mortals, though designed to be smaller in both horizontal directions and without the shelves in the middle.
I built a bench out of some scrap lumber. I made it "narrow-stance" to allow for the severely rounded edges on the two pieces of 2x6. As is often the case, I made some changes to the design while I was building it (turned the legs 90 degrees for better stability in the real world).
I keep a lot of large cardboard boxes and styrofoam on hand for when I need to ship my paintings.  I needed a simple shelf for containing the large cardboard.  I built a very simple one in less than 2 days.
For my office space, I designed a desktop to fill the 10-1/2 foot space from one wall to the other.  At the outside edges, the desk is almost 4 feet deep, and then angles towards a 29" deep center section.  I designed it to fit snugly on top of some store-bought rubberwood cabinets.
I designed a pergola for the new deck we were having built.  I used a 3D program, AC3D, that works like Lightwave, but is much simpler at a fraction of the cost.
Design Inspirations
Window greenhouse