A lot of really nice things have been made from the skeleton of the Cholla cactus (say choy a) things like knife handles and cool looking lamps. Large floor lamps have been made from the Saguaro skeleton. Most cacti have hollow cylindrical lattice like woody skeletons. Most cacti are protected and the only way to get the "wood" is to look for naturally dead plants that the soft parts have rotted away from leaving the wood.
Ex-Desert Rat,
Gabby