Getting Started
You may want to start with the tkdocs Tutorial.
How to write and run the_simplest_possible_Tkinter_program.
Stephen Ferg has written a good introduction called "Thinking in Tkinter" that looks at Tkinter from the point of view of common conceptual difficulties that the beginner faces. --SAM
Examples and Help.
Using IDLE to Edit/Test Tkinter Programs
Starting with Python version 2.3, you can use the IDLE text editor/debugger to edit and test Tkinter programs. IDLE itself is written in Tkinter, and you can even look at its source code to find examples of how to do things in Tkinter.
If you are using an earlier version of Python that includes IDLE 0.8, you cannot use the root.mainloop() command in a program being run in IDLE. If you do, it will hang, because IDLE used the same Python interpreter process (and therefore the same Tkinter event loop) as the program being tested. You can test your program in IDLE 0.8 by commenting out the ".mainloop()" call, but then you need to be sure to un-comment it before using the program elsewhere.