Installing eclipse and pydev is done from synaptic and is straight-forward. Installing pydev extensions happens from Help > Software Updates > Find and Install > Search for new features to install. Have a remote site of http://pydev.sourceforge.net/updates/

NB we only want pydev, not the optional pydev mylyn integration (if you get nagged for things about mylyn you forgot to uncheck that part 😉 ).

When installing plugins, start eclipse from the terminal as root
sudo eclipse
otherwise you lack the rights to add certain folders etc. See http://ubuntuforums.org/showthread.php?t=568894.

Then set interpreter for python: Window > Preferences > PyDev > Interpreter – Python > New
to /usr/bin/python2.5 etc.