Tkinter is Python's de-facto standard GUI (Graphical User Interface) package. It is a thin object-oriented layer on top of Tcl/[http://wiki.tcl.tk/tk Tk].
Tkinter is not the only GuiProgramming toolkit for Python. It is however the most commonly used one, and almost the only one that is portable between Unix, Mac and Windows. CameronLaird calls the yearly decision to keep TkInter "one of the minor traditions of the Python world."
More info here: http://www.python.org/topics/tkinter/
A new Tkinter wiki: http://tkinter.unpythonic.net/wiki/
[http://www.astro.washington.edu/owen/TkinterSummary.html Tkinter Summary]
[http://www.astro.washington.edu/owen/ROTKFolklore.html Tkinter Folklore]
David McNab recommended the latter two as particularly "pythonic" in not insisting that readers think in Tcl.
- ["How Tkinter can exploit Tcl/Tk extensions"]