Borland has released their latest compiler for free. This distribution only includes the command-level tools and not the IDE. It can be obtained at http://www.borland.com/downloads/download_cbuilder.html
Code::Blocks is a free C++ IDE.
Microsoft released a free version of their Microsoft C/C++ Optimizing Compiler and Linker. It includes the C Runtime Library and the C++ Standard Library, including the Standard Template Library, and the Microsoft .NET Framework Common Language Runtime. See http://www.microsoft.com/express/vc/
Also one needs to install the [Microsoft Platform SDK]
VIDE is a GUI development environment that supports the Borland C++ 5.5 command line compiler above. It also can be configured to run with the Cygwin or MinGW? gcc and gdb as well as java compilers. It can be found at http://www.objectcentral.com/
A complete port of major Unix utilities and emulation of Posix functionality for all versions of Windows since Win95, except for Windows CE. It seems to work best on NT kernels. Includes gcc, binutils, shellutils, fileutils, textutils, flex, bison, make, awk, etc. Has nice setup tool that allows package installation and deinstallation. It can be found at http://www.cygwin.com/
A C compiler for Win32 systems. Not a bad compiler at all. Pretty fast and competitive with the big boys. It comes with a very nice feature rich editor that has things you wouldn't normally expect. It's worth checking out even if you don't use the compiler. It can be found at http://www.cs.virginia.edu/~lcc-win32/
A free 32-bit C compiler for DOS. This site also has links to DOS sockets stacks. Yes Virginia, you can even run a internet connected mud on DOS too. It can be found at http://www.delorie.com/
Digital Mars C and C++ Compilers for Win32, Win16, DOS32 and DOS. Great potential. Author has tons of compiler experience. Also a language called D may be found here. It can be found at http://www.digitalmars.com/
MinGW is a collection of freely available and freely distributable Windows specific header files and import libraries combined with GNU toolsets that allow one to produce native Windows programs that do not rely on any 3rd-party C runtime DLLs. MSYS is a Minimal SYStem to provide POSIX - Bourne configure scripts the ability to execute and create a Makefile used by make. http://www.mingw.org/
Yet another port of gcc to Windows. They've also ported gnu pascal. It can be found at http://www.bloodshed.net/
Activestate Perl for Win95/NT. It can be found at http://www.activestate.com/Products/ActivePerl/
Perl distributions also exist for Cygwin and MinGW?
Python is an interpreted, interactive, object-oriented programming language. It is often compared to Tcl, Perl, Scheme or Java. The Python implementation is portable: it runs on many brands of UNIX, on Windows, OS/2, Mac, Amiga, and many other platforms. http://www.python.org/
Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, extensible, and portable. There's a one-click Windows installation, and one can also compile it with BC++, VC++, MinGW?, and Cygwin. Exists as a Cygwin package (see above). http://www.ruby-lang.org/en/ - I like it a lot.
Crimson Editor is a professional source editor for Windows. This program is not only fast in loading time, but also small in size (so small that it can be copied in one floppy disk). It handles remote editing and multiple language formats and syntaxen. It can be found at http://www.crimsoneditor.com/
TextPad? is a powerful, general purpose editor for plain text files. Easy to use, with all the features a power user requires. Not a bad editor. Understands mac, unix, dos and windows textfiles. http://www.textpad.com/
A free source code editor for Win32 and X. Very nice set of features. http://www.scintilla.org/SciTE.html
A free notepad replacement/source code editor for Win32. GPL'ed. Includes syntax highlighting for many common languages as well as other features and supports plugins, themes. http://notepad-plus.sourceforge.net/uk/site.htm