- Steampunk: Victorian technology; powered by steam and gears and the like.
- Clockpunk: Rennaissance technology; powered by pendulums and gears; very inspired by the concepts of Leonard da Vinci.
- Dieselpunk: Technology from the early days of locomotive travel; powered by, obviously, diesel and very much dependent on combustion, heat, and iron.
- Atompunk: An essentially purely conceptual sub-genre based on the extrapolation of the atomic power craze in the 1960's; powered by nuclear reactions.
I admit that there are likely others, but this is an overview of the most basic retrofuturism sub-genres. For a much more complete explanation feel free to check out the Wikipedia page for Retrofuturism and follow the lovely links.