4 Open Source Compilers for Developers

1. DotGNU Portable.NET
Intended as a replacement for Microsoft's .Net, DotGNU provides a variety of tools to compile and run applications. It currently supports C and C#. Operating System: Windows, Linux, OS X. The initial target platform was GNU/Linux, but DotGNU Portable.NET has been known to work under Windows, NetBSD, FreeBSD, Solaris, and MacOS X, amongst others. It also runs on a variety of CPUs including x86, PPC, ARM, Sparc, s390, Alpha, ia-64, and PARISC

2. GCC

The "GNU Compiler Collection" offers front ends and libraries for C, C++, Objective-C, Fortran, Java, and Ada. It's probably the most widely used compiler for code that will run on multiple operating systems. Operating System: OS Independent.

3. MinGW

"Minimalist GNU for Windows" ports the GCC compilers and GNU Binutils for Windows. It allows you to use GNU tools to build Windows apps from Windows or Linux systems. Operating System: Windows, Linux

Open64: Formerly known as Pro64, Open64 was created by Intel and the Chinese Academy of Sciences. It includes compilers for C, C+