I recently got into cycling and got interested in tracking my performance to improve my ride. I couldn't find an affordable bike computer that I could easily modify so I built my own. One thing lead to another and I found myself building an electronic derailleur. I thought others might be interested in doing the same so I wrote an instructable. Love to know what you think. If you like it please vote.
http://www.instructables.com/id/DIY-Electronic-Derailleur/?ALLSTEPS
The Arduino sketch, schematics, Fritzing diagram, bill of materials and CAD diagrams can be found on the project page http://nabilt.github.com/diy_eshift/.
The next version will include GPS, accelerometer, altitude sensor and more http://www.nabiltewolde.com/2011/11/bike-computer-v01-build.html