MiniINI is a a free/open source (X11/MIT License), minimalistic, fast and simple to use C++ library for reading ini (or cfg) files. It has no dependencies and should compile on any platform with a standard compliant C++ compiler (although it requires C99 support).
The goal of MiniINI is not to support a myriad of extensions to the common INI format, but to be easy to use and to read (and, in future, write) ini files as quickly as possible.