I've had a number of requests to recommend some Python IDEs. Although I don't use a Python IDE myself (just a good programmer's editor) I have heard others speak highly of several.
WingIDE is a commercial product and has an extremely solid reputation. It is cross-platform, although it requires X11 on Mac OS X.
Komodo is another cross-platform commercial product with very good reviews, and it doesn't require X11 on Mac OS X.
SPE is free and highly-recommended by many, although the web site seems to be down as I write.
The Python Wiki has a long list of Python editors and IDEs, although having such a long list without any rating system makes it difficult to find what you are looking for.