From http://www.tcl.tk/
Tcl (Tool Command Language) is a very powerful but easy to learn dynamic programming language, suitable for a very wide range of uses, including web and desktop applications, networking, administration, testing and many more. Open source and business-friendly, Tcl is a mature yet evolving language that is truly cross platform, easily deployed and highly extensible.

Tk is a graphical user interface toolkit that takes developing desktop applications to a higher level than conventional approaches. Tk is the standard GUI not only for Tcl, but for many other dynamic languages, and can produce rich, native applications that run unchanged across Windows, Mac OS X, Linux and more.

These programming languages, getting into the basic "Hello World!" type examples and some basic syntax, seem very versatile and fun. I'm starting learning TCL from http://www.invece.org/tclwise/frontcover.html but I'm still looking for a good TK tutorial.