MinGW - GNU Compilers and Tools on Windows

MinGW is a collection of freely available and freely distributable Windows specific header files and import libraries, augmenting the GNU Compiler Collection, (GCC), and its associated tools, (GNU binutils). MinGW provides a complete Open Source programming tool set which is suitable for the development of native Windows programs that do not depend on any 3rd-party C runtime DLLs.

http://cplus.about.com/gi/dynamic/offsite.htm?zi=1/XJ/Ya&sdn=cplus&zu=http%3A%2F%2Fwww.mingw.org%2F