Mingw-w64 is an advancement of the original mingw.org project, created to support the GCC compiler on Windows systems. It has forked it in 2007 in order to provide support for 64 bits and new APIs. It has since then gained widespread use and distribution.
The development and community are very active and welcoming with new contributors every month and simple installers.
You can also look at the full list of versions.
Mingw-w64 interacts a lot with other projects in order to help everyone move forward. Contributions have been going to and coming from these projects:
Update to autoconf v2.69 (aka automake 1.15)
Merge branch 'master' of git://git.code.sf.net/...
typo in _pthread_tryjoin() fixed & warn about "...
Fixes warning when wchar_t is used