The documentation for the various libraries is a bit scattered. Here is a partially-complete list:
A general scheme of Rosetta source code organization
Large size file (poster size) can be downloaded from here
src index page - Overview of the src directory.
Tracer - Using the tracer output class.
Hbonds - Dealing with the Hbond energy terms.
namespace-core-fragments - Using the classed located in src/core/fragments/
xyzVector - A vector specialized for Cartesian coordinate use.
xyzMatrix - A 3x3 matrix class specialized for Cartesian coordinate use.