A collection of fascinating bitters recipes, mostly from Chow:

Aromatic: http://www.chow.com/recipes/12039-aromatic-bitters

Orange: http://www.chow.com/recipes/12038-orange-bitters

Grapefruit: http://www.chow.com/recipes/11285-grapefruit-bitters

Cardamon/Saffron: http://www.chow.com/recipes/11279-sunshine-bitters