Preferably one that can do auto completion on the modules that come with Maya and Houdini.
Paul Nendick
[ Editor ]
Even the basic python interpreter can tell you about the modules you're using:
$ import Maya
$ help(Maya)
$ dir(MAYA)
That said, my favourite set up generally is Eclipse + PyDev extensions. It gives a full IDE environment plus debugging with check-pointing, stack inspection, module completion; the lot. It's pretty easy to get going on Linux with a proper package manager.
Here's a good (on Windows) setup guide: http://www.vogella.de/articles/Python/article.html
For just small tasks, I prefer 'scite' (GUI) and 'iPython' (command-line). Scite runs your coding-in-progress in a command buffer by hitting 'F5' and iPython has code-completion and other goodies like proper tab/white-space handling. iPython is probably the best 'hard-core' tool of the lot.
Editra is what I use when I'm on a Mac or Windows. It's a lot like Scite.
IntelliJ if it's got better Python support would be the best of the lot. It is an absolutely wicked Java tool for messy things like refactoring. I haven't tried it in a couple years.
Netbeans has some Python support these days that might be nice. I got burnt by that tool ages ago and won't look back. The same goes for Xcode.
Finally, here's what our 'sister' site had to say: http://stackoverflow.com/questions/81584 /p
ps: vi, not emacs :D
EDIT: There's a new/cool looking Python IDE on the scene: http://www.jetbrains.net/confluence/display/PYH/JetBrains+PyCharm+Preview

Thanks Paul,
Eclipse is what most people here at work use. I’m gonna give that a go.
It is definitely going to be painful to start with Eclipse as it’s a bit of a beast. Do stick it out, it’s worth the effort. Post any problems here and we’ll do our best to get you through it. Good luck!
– interested to hear why you wouldn’t go near XCode again? I used XCode for a while. I really liked the debugging tools and still use it as a UI for GDB. For everything else now I use TextMate.
I still kinda like XCode for Mac-only C/C++/Obj-C coding (are there any other options really?) but for Python not so much. Any Python I do on a Mac tends to need to work on Linux too and at some point I got fed up with Apple’s bizarre interpretation of standard UNIX path structure. Once I ditched that and started installing Python on our Mac systems in a more logical fashion, XCode starting fighting back and refusing to load the libraries that weren’t where it expected them. So I just drop into
viandiPythonnow and all is well. Or TextMate. Actually I haven’t used XCode for ages now…– don’t forget to click the tick if it answer answers your question well. you get 2 rep.