Colin - CDU.
Philip - certainly wouldn't "belong" to a party, but would vote CDU or FDP if bothered to vote.
Could it be generalized this way?:
--> Republicans: CDU/CSU
--> Libertarians and libertarian-leaning Republicans: FDP
--> centrist Democrats: CDU/CSU (or possibly FDP?)
--> liberal Democrats: SPD or Greens
--> very liberal Democrats (BRTD-style ): PDS
Add
--> Populist Democrats: SPD; and for some of them possibly far right "protest".
--> Populist-leaning Republicans: SPD or CDU, depending on regional and family traditions, and indirectly confession (Protestant implies SPD, Catholic implies CDU); and possibly far right "protest".
--> Populist Democrats (East Germany): PDS