Using a Varde birch countertop (roughly 50″x25″), four of the single-cube Expedit units, and eight 4-inch Capita legs, I built this unit which suits my wife well. It stands about 38.5″ high and, between the shelving units, includes just enough space for an Ingolf bar stool, which comes in handy when she prefers to sit. A 1×3″ board joins the Expedit units in the back, and a series of straight and L-shaped brackets hold the unit together securely.
Possible improvements (which I may someday get around to making) include the installation of a drawer unit in at least one of the cubbies, as well as a backing board to hide the cables and cords that drop behind the desk.
The cost of this project breaks down roughly as follows:
Varde countertop: $80
Expedit cubes: $40 (on sale for $10/each when I bought them)
Capita legs: $24 (two packs at $12/each)
1×3″ board: less than $10
Various brackets and screws: less than $10.