These are the stock shelves by the garage door at Emeryville Squidlabs.
Look carefully. This is a very strong set of shelves made without any rabbets or mortises.
The whole thing can be made very quickly with repeated square cuts.
The vertical boards are 3/4" plywood with 3/4" square plywood cheekpieces sandwiched against them.
The ends of the 2"X10" shelves are inserted in the gaps between these square cheekpieces.
The 1"X2" end caps on the verticals keep the shelves constrained horizontally and stiffen the verticals further. The top of this shelving unit supports a storage loft.