In November 2008 I happened across some MadCatz driving pedals at the recycling shop at the local tip.
I modified the pedals and placed them on a wooden frame, then connected them to my PC via a gameport interface.
I was able to very inexpensively create a set of rudder pedals that included differential braking. These pedals worked a lot better than my first attempt at pedals.
This is a YouTube video about my homemade rudder pedals: