The following resources provide an excellent complement to the documentation offered by this chapter. They link to several Tk/Tkinter related sites.
Tkinter
http://www.python.org/topics/tkinter/
Matt Conway's Tkinter Life Preserver
http://www.python.org/doc/life-preserver/index.html
Tkinter Standard Dialogues
http://starship.python.net/crew/fredrik/py14/tkdialogs.htm
Tkinter: GUI programming with Python
http://www.nmt.edu/tcc/help/lang/python/tkinter.html
Python and Tkinter Programming, by John E. Grayson
http://www.manning.com/Grayson/Contents.html
An Introduction to Tkinter, by Fredrik Lundh
http://www.pythonware.com/library/tkinter/introduction/index.htm
Tkinter Class Reference Pages
http://www.pythonware.com/library/tkinter/tkclass/index.htm
Online Tcl/Tk Manual Pages—the official man pages at Scriptics
http://dev.scriptics.com/man/
Tk 8.0 man pages
http://dev.scriptics.com/man/tcl8.0/TkCmd/contents.htm
Ajuba (formerly Scriptics)—the company founded by Tcl/Tk's inventor, John Ousterhout
http://www.ajubasolutions.com/
Vaults of Parnassus—User Interfaces and Widgets Section
http://www.vex.net/parnassus/