GloWorm
A Firebug-like tool that allows you to delve into the code (TAL, METAL, Python) underlying your site. A point-and-click interface lets you highlight something on your screen and see what template or script produced it. Reorder, show/hide, and edit viewlets inline. Currently in beta stage.
The link address is: http://pypi.python.org/pypi/Products.Gloworm
