You can install the latest “nightly build” version of SunPy from GitHub. GitHub provides a convienient download link. It may be easier in the long run to grab SunPy using Git, a light and easy version control system:
git clone git://git@github.com/sunpy/sunpy.git
If you are using Python 2, you can use paver to create a link to the SunPy directory you just downloaded in a location that is accessible to Python:
sudo paver develop
This will make it make possible to import and use SunPy from anywhere on your system. Alternatively, if you would prefer you can also skip the paver step and simply include SunPy locally by starting an interactive Python session from the root SunPy directory.
SunPy also supports installation for Python 3. Instead of using paver develop, however, you must instead perform a more routine installation using setup.py. Additionally, it is recommended that you first install the Python distribute package before installing SunPy.