Compilers
Free
C
TCC: Tiny C Compiler licentie: LGPL.
pcc - Portable C Compiler licentie: BSD-style.
vbcc - portable ISO C compiler
GCC
MinGW, a contraction of “Minimalist GNU for Windows”, is a minimalist development environment for native Microsoft Windows applications.
MinGW-w64 The project's goal is to deliver runtime, headers, and libs for developing 64 bit (x64), as well as 32 bit (x86), windows applications using gcc-4.6 or newer versions.
TDM-GCC is a compiler suite for Windows. It combines the most recent stable release of the GCC toolset with the free and open-source MinGW or MinGW-w64 runtime APIs to create a LIBRE alternative to Microsoft's compiler and platform SDK. It can create 32-bit OR 64-bit binaries, for any version of Windows since Windows 95.
MinGW Distro - nuwen.net a MinGW distribution.