Procedural generation has been brought into the spotlight recently (by Spore, MMOs, etc), and it seems like an interesting/powerful programming technique.
My questio
If you want an example of a world generator simulation plates tectonics, erosion, rain-shadow, etc. take a look at: https://github.com/ftomassetti/lands
On top of that there is also a civilizations evolution simulator:
https://github.com/ftomassetti/civs
A blog full on interesting resource is:
dungeonleague.com/
It is abandoned now but you should read all its posts