Pallet wood like urbanite stone is quite plentiful in our world even as our other resources dwindle. (Urbanite is the natural builder's nickname for discarded concrete while pallet wood is any wood recovered from shipping pallets.)
Architect Alfred von Bachmayr , founder of World Hands Project has experimented with building trusses from discarded pallets. His work was inspired in part by the ingenious use of pallets by the residents of Juarez, Mexico. He has found that many different truss configurations are possible. Possible designs include a gable truss, one with a flat bottom chord and sloping top chord and non-symmetrical shapes.
The Pallet Truss: A Low Cost Alternative Roof Structure on the Builders Without Borders site can give you an introduction to his findings. More information and photos are included in the book Building Without Borders edited by Joseph Kennedy, a Google book preview of which is available on the web.
The Geiger Research Institute has developed a variation on von Bachmayr's work which mainly uses pine poles in place of pallet sections for the top and bottom chords of the truss.
Yet another variation is used for straw bale structures as pictured here.