http://thule.mt.cs.cmu.edu:8001/sf-clearing-house/bibliographies/alternate-histories/
The Alternate History WWW site houses the archives and other resources for the discussion group of the same name which focuses on allohistories (a.k.a. what-ifs, and counterfactuals), or writings in which a past event is altered and its effect on later history is somehow described. Contents are archived according to author, reference material, introduction.