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.
The Zenautics Matrix Project is a matrix/vector class for C++. It supports real and complex data for nearly all matrix algebra calculations. It is optimized for the double type (std::complex). It works well with small and large matrices. It is easy to use and get started. It features plotting, FFT/IFFT, and more.
KitClasses are a collection of add-on classes for KDE application development. The library consists of classes that range from simple sub-classed enhancements to complex, full-featured widgets. The goal of this project is to develop quality complex widgets that will easily plug-in to developers' applications.