Latest stable branch of wxPython.

From the home page:
  wxPython is a GUI toolkit for the Python programming language. It allows
  Python programmers to create programs with a robust, highly functional
  graphical user interface, simply and easily. It is implemented as a Python
  extension module (native code) that wraps the popular wxWidgets cross-
  platform GUI library, which is written in C++.

  wxPython is a cross-platform toolkit. This means that the same program
  will run on multiple platforms without modification. Currently supported
  platforms are Microsoft Windows, and most Unix or Unix-like systems.

WWW: http://www.wxpython.org/