Doxygen is a tool for generating documentation from annotated C++ sources, as well as other popular programming languages like C, Objective-C, C#, PHP, Java, Python, IDL (CORBA, Microsoft, and UNO/OpenOffice flavors), Fortran, VHDL, Tcl, and to some extent D.
It's not, well not compared to the original code it was ported from. The original API viewer is here (also, many thanks to wkeese for writing the dapi exporter for js-doc-parse which makes loading and parsing a breeze compared to loading/parsing XML).
LuaDoc is a documentation generator tool for Lua source code. It parses the declarations and documentation comments in a set of Lua source files and produces a set of XHTML pages describing the commented declarations and functions.
Building APIs redefined. Speed up development of services, mobile, and web applications with auto-generated client, server, and documentation in many languages. Cut the costs and development time by up to 50%.