@cfrank Good question. I'm not sure I can think of one place that gives a good intro to all the stuff. Anything I know I've picked up piecemeal over the years, and there isn't really that much about proportional cardinal methods in general I'd say. The stuff on the Electowiki could probably do with being massively overhauled.
Obviously the Thiele and Phragmén methods have been around for over a century but academic research into this type of method only really picked up again relatively recently, and dry academic papers aren't the best place for a beginner to learn about them anyway.
Edit - Maybe I could start a thread with some basic info. Others can add to it and can also take issue with anything they might disagree with!