Have you ever been interested in what extensions are available for Firebug? If yes, take a look at what I have found. Frankly, I was quite surprised how many Firebug extensions already exists out there.
WSUnit - The Web Services Testing Tool
WSUnit is a tool that can help you test Web Service consumers. It provides a predictable and repeatable simulation of a Web Service that is ideal for unit testing. It is also useful when developing web service consumers when the actual web service may not be avaliable due to your remote location or may not have been fully developed itself.
PyDev is a plugin that enables users to use Eclipse for Python and Jython development -- making Eclipse a first class Python IDE -- It comes with many goodies such as code completion, syntax highlighting, syntax analysis, refactor, debug and many others. If you want more details on the provided features, you can check here.
How can people still build software without seeing its real structure? After a compiler and a text editor, a dependency viewer is the first thing you want. Byecycle is the requisite dependency viewer for Eclipse.