MinGW: 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.
[incr Tcl] is the most widely used O-O system for Tcl. The name is a play on C++, and [incr Tcl] provides a similar object model, including multiple inheritence and public and private classes and variables.