I use Komodo Edit (like a lot of others here). The toolbox feature is kinda handy too, you can put commonly used commands in the toolbox and just double click them to run on the current script. Currently I've got a python script that automatically ftp's the file I'm working on to a specified directory and one that launches the current script into WinPDB which is quite simply the best debugger I've ever used. http://winpdb.org/
Some people have a great ambition: to build something that will last, at least until they've finished building it.