Containers to extend STL: graph, tree, matrix, smart-pointer. Persistence (serialisation) of C++ data structures. Portability: subprocesses, TCP, file system. Reusable subsystems: library manager, message handler. Portable between OSs and compilers.
Documentation is included in the download and is also available on the STLplus website http://stlplus.sourceforge.net. The headers are intended to be readable, so look at them too for usage information on each function and class.
Embedded HTTP Server (EHS) is a C++ class library which can be inherited from to add HTTP(S) server functionality to any class or application. It is easily extendable (samples included) and supports SSL, form data via POST or GET, uploads via multi-part form attachments and WebSockets. Operation modes include single- and multi-threaded operation.