Standard C++ Library
Containers to extend STL: graph, tree, matrix, smart-pointer. Persistence (serialisation) of C++ data structures. Portability: subprocesses, TCP, file system. Reusable subsystems. Documentation is included in the download. The headers are intended to be readable, so look at them too for usage information on each function and class.
Source-Code: https://sourceforge.net/projects/stlplus/