Points of divergence dealing with the geography (and geology) of planet Earth itself.
Avalonia Alone - This one concerns how civilisation would have developed if Avalonia did not break up and remained a separate island in the middle of the Atlantic.
The Rise of Gondwana - Discussion about a geological POD in which Australia and Antarctica remain fused together as a single continent. Started by Danbensen, who has been working on such a project in his free time, outside of the AH.com board.
Know of any PODs or POD discussions ? Feel free to add them.