ORIGINAL: RCVFR
I have made several sets of standoffs from round dowel, and then I saw one of T.O.M.s earlier posts about using square stock. I found the square stock much easier to work with and get good accuracy in my measurements. It's what I use, now for standoffs greater than 1/2'' or so.
Another benefit of that method is the ability to glue on lite-ply sides for added rigidity