In my python-mode-hooks I have:
* rainbow-mode (if hex colour codes are detected in strings, emacs colours the string appropriately). Not terribly useful, and I was surprised it was still there when I checked my hooks just now!
* flymake-mode (hooked up to flymake-pyflakes). Tells me about unused imports and unknown/unused variables.
* rainbow-delimiters-mode. Colours nested matching parenthesis. They don't show up in my code very often, and I just threw this in for the hell of it, after tinkering on some elisp.
* linum-on. I don't have global-linum-mode enabled, preferring to only enable it for buffers containing actual code.
* jedi:setup. Install it from ELPA with “M-x package-install<RET>jedi”. This one is pretty cool, and hooks up Emacs' builtin autocomplete to provide proper python autocomplete based on code introspection. Docstring integration is nice, too.
Some other little bits and bobs:
* customised `line-spacing' to 1: puts some more space between lines, which I like.
* customised `global-hl-line-mode' so I can find the point more easily.