** Update 10/8/2013 **
Now I am using jedi-driven vyth vim configuration (along with some tmux configuration)
https://github.com/JarrodCTaylor/imt_dotfiles
I also have a pretty complete vim configuration for django development (if you're interested).
https://github.com/toranb/vimfiles
I use rope-vim as mentioned by others, but I also have some other useful plugins so you can run unit tests (using the nose) in a django project with QTPY
A few things that I came across are that others, as a rule, are not mentioned when developing python / django on OSX and Ubuntu (dev / night time dev / dev), including:
https://github.com/lambdalisue/vim-django-support
https://github.com/jmcantrell/vim-virtualenv
If you make sure that vim has activated virtualenv (assuming you use virtualenv), the plugin will know where to find the packages for your site to quickly "go to definition" along with other refactoring support.
I use this without any need for pycharm, since I get full completion with rope-vim and supertab. I also have a command-t plugin to quickly find "find by file" / etc
I recently discovered that using basic ctags on OSX + Ubuntu allowed me to “find a character” using the below. I also added a simple search for “recent files” using find in the buffer. I also added some shortcuts to show a fuzzy search, for example, a search from the current directory (for a file that I think is open). I use this to quickly show other related / etc files.
find by equiv symbol (shows classes / methods in fuzzy finder using your ctags file)
:FufTag
find in buffer (latest files)
:FufBuffer
show fuzzy search with other files in the current directory
:FufFileWithCurrentBufferDir