I purchased 1/4" exterior plywood in 4x8 foot sheets.
With the first sheet of plywood you can cut out two side pieces and two transoms (the back end of the boat). Measure carefully and you'll be fine. Refer to Hannu's diagrams for dimensions. The first boat I made was the larger of the two.
I used a skill saw and sawhorses to cut the sides and transoms out of the wood.
Since I was already cutting, I used the last two pieces of plywood to cut the sides for the second, smaller boat sides. I kept the larger remains of both sheets of ply to cut the bottom of the boat from.
To save yourself some time in the long run, I suggest you order your oarlocks now. By the time they reach you the boat may be ready.
I found a decent deal at www.shipstore.com, specifically this item:http://www.shipstore.com/SS/HTML/ATT/ATT91463.html
This turned out to be the only real hardware I couldn't make myself.