For all the mechanical clumsiness involved in yanking a chain from one sprocket to another, derailleurs are beautiful and clever pieces of engineering. I’ve collected together some of what I think are the cleverest designs...

Suntour: Even at their peak, Suntour were much smaller than Shimano - but even so they managed to invent a lot of the features that all manufacturers now use. The pinnacle of this was the sloping parallelogram patented by Suntour in 1964, which allowed derailleurs to cover a much wider range of sprockets. Until this patent lapsed in 1984, Suntour made what were regarded as the best derailleurs on the planet.

Shimano: I couldn’t have a derailleur museum and miss out the largest manufacturer! Suntour’s patent cast a long shadow over Shimano, though, so it’s interesting to look at the derailleurs Shimano made during the same period.

Other Derailleurs: In no especial order, I’ve got a couple of interesting Huret derailleurs, an all-plastic Simplex from the early ‘60s, and a very light Mavic derailleur...

For the definitive history of the derailleur, you really need to get “The Dancing Chain” by Frank Berto et al - incredible detail on derailleurs from the very beginning:

http://www.cyclepublishing.com/cyclingbooks/dc.html