The Python Wiki has a nice list:
Most of the home pages for those libraries have screen shots and samples you can run after downloading the library.
I've used wxPython with success and like it a fair bit. I also hear good thing about PyQT constantly. Both can be used to produce well finished products, I think.
Some more information on both PyQT and wxPython is available on the Python Wiki:
Both libraries have their own license and I'm afraid I can't tell you much more about that. (I know you can get a commercial license for PyQT, but do not know the costs involved.)