SPIN_py is a Python module that wraps the SP SGML parser. It does not follow SAX, nor DSSL, but it performs a similar task. It has code to build (and pretty-print) trees from C++ or from Python, and it has an interesting object model, with virtual C++ objects, based on PyObject_HEAD.
IoBind uses meta-programming and policies to create readers and writers for complex objects at compile time. In other words, it is a code factory that produces customized readers and writers; you give the action to take and the objects to process, and it will generate the corresponding code: STL containers, uBLAS matrices, etc.