I have joined a mailing list called Helicopterview. It was set up recently following a thread on ILX about how it would be nice to have somewhere to talk seriously about politics.
At the moment the list is small and invitational. If you are interested in joining it then I suppose the best thing you could do is go to the original ILX thread "Where do you go to discuss politics?" and either post there expressing interest or e-mail Catherine Leech, the threadstarter.
The list archives are not currently online.