While organinzing the other day I ran across a booklet by the Singer Company, "How to Make Slip Covers", from 1961. It caught me at a weak moment and I decided to try doing a simple slipper type chair. Two days later -->
As far as I can tell, fitted slip covers use more or less the same amount of fabric as re-upholstering, the advantage being they can be removed and washed. While I wouldn't say that making a slip cover is for the faint of heart - mistakes can be costly - it's certainly doable with some sewing skills and plenty of time. I thought the booklet helped understand the process much better than the patterns you can buy.
Looking around, I now have thoughts of "covering" 5 more chairs and 2 couches. First I have a some hemming and a zipper to install. Wish me luck!