Tcl is one of the most underrated computer languages today.
It has a weird syntax, but on the other hand the syntax makes it more extensible than any other language besides the Lisp family.
Tk is reputed for it's antique-looking widgets. However with the latest 8.5 releast TTk, Themeable Tk is the default which means native look on Vista, XP, OSX. (Not Linux though, but what can you call native there anyway?)
So if you don't know Tcl yet, go and learn it. It's extremely simple, has an interactive shell, and will expand your mind... much more than learning most other languages!!
Tcl/Tk rocks!