There is an ibook "the art of moving points" by Brian Tindall. It comes with a bunch of videos with further explanations. You can find a few examples here:
It also covers modelling and is not application specific.
Not really rigging books, but I always have those on my desk and look things up in them more frequently than in any rigging book I read so far.
"3D Math Primer for Graphics and Game Development" - Ian Parberry
"Animal Anatomy for Artists" - Eliot Goldfinger
"Practical Maya Programming with Python" - Robert Galanakis
"Classic Human Anatomy" - Valerie Winslow