The Widget Construction Kit (WCK) is an extension API that allows you to implement custom widgets in pure Python. The WCK can be (and is being) used for everything from light-weight display widgets to full-blown editor frameworks.
The Tkinter3000 implementation of the WCK supports all recent versions of Python and Tk/Tkinter.
The 1.1 beta 1 release adds improved controller support, resource caching for pens, brushes, and fonts, and support for creating image objects from data in strings.
Using WCK and AggDraw to draw anti-aliased graphics: http://www.effbot.org/zone/wck-aggview.htm