I recently heard a report on "the splendid table" about Dr. Levine at the Mayo Clinic and his treadmill desks:
Right away the next day I made stands for my two non-standing desks, so that I could use them as treadmill-desks if needed.
2 x 4 (8 feet or so)
2 x 1/2" (8 feet)
saw (I like the japanese pulling saws)
screwdriver (or screwdriver drill)
drill and small bit (for pre-drilling screws)