Political affiliation would be cool. Here's a good place to start as far as a basic list:
Left -
http://en.wikipedia.org/wiki/Left-wing_politics
Liberalism -
http://en.wikipedia.org/wiki/Liberal..._United_States - Includes Classical liberalism, Populism, Marxism, Green politics ect..)
Right -
http://en.wikipedia.org/wiki/Right-wing_politics
Conservatism -
http://en.wikipedia.org/wiki/Conservatism - Includes subcatagories like Neoconservatism, Social Conservatism, Paleoconservatism ect..)
Centrist (Syncretic politics) -
http://en.wikipedia.org/wiki/Syncretic_politics
Libertarianism -
http://en.wikipedia.org/wiki/Libertarianism
The links contain extensive information on all the sub-categories as well.
You might even want to make a sticky read-only post in one of the main forums with links to explanations and details for the various ideologies (links don't have to be to wikipedia articles necessarily, though wikipedia is probably one of the best sources for stuff like this). It might seem overly involved, but as we all know, there have been some very long threads about this kinda stuff before.
Would be nice if there was a One-Stop-Shop on here with source material on the various wavelengths of the Political spectrum. Would be especially useful to new people to give them a broad overview. I would be happy to make a template if you want. You (or the moderators) could always change or expand it as the need arises.