Why won't pip install anything?
Following @HugoTavares's suggestion I found I needed to install python-dev. I don't know why this helped but it seems to have solved this particular problem. I'm putting this answer on for now but Hugo, if you read this, please post an identical one and I'll remove acceptance on this and accept yours, since you deserve the credit.
Whenever I try to pip install anything in my virtualenvs I am told it is Downloading/Unpacking. My terminal then stays on that line indefinitely. The longest I have left this running was 2 hours (trying to install iPython) without success.
Most recently, I tried installing django in one virtualenv using pip. Once it said Downloading/Unpacking I created another virtualenv in another terminal window and used easy-install to install django and mezzanine. Both installed with their dependencies before there was any movement on the terminal using pip. I left the pip window running for an hour before giving up. I have tried pip install, pip install -v --use-mirrors and their sudo equivalents without much change in the results (-v --use-mirrors spews out a list of urls before stalling at Downloading/Unpacking).
I am using Python 2.7 on Ubuntu 12.04.1 64-bit. I use Virtuanlenvwrapper to create and manage my virtualenvs, if that helps.
I can't find any references to other people having this problem so I expect it's a mistake of mine. Does anyone have any idea what I'm doing wrong?