This simple wooden box is part of the Crate series by London designer Jasper Morrison. It's made of Douglas fir and, as the designer suggests, "is suited to many applications such as a bedside table, storage or occasional table."
It doesn't seem like the series is available for purchase anymore...which is okay, cost it was pretty costly. Doug fir is incredibly affordable and very easy to work. The genius of these boxes is the solid back panel, which provides lots of rigidity and allows the crates to be used for storage in multiple configurations.
Of course, fir is a softwood, and if you really wanted these to be secure (say for sitting) you'd want to up the joinery to something more than just butt joints (Morrison's design used box joints). But for lightweight use, you could assembly one of these with $20 worth of wood, plenty of glue, and a simple handsaw. Grab some clamps, and go.