I've been trying to install plugins and find updates in Eclipse today without any success. I've never had any problems with this before. I first tried Helios but after a while I gave up and downloaded Juno which exhibits the same behavior:
When trying to connect to Juno's update site (http://download.eclipse.org/releases/juno/), Eclipse hangs while "fetching its children". I did my research and tried several suggestions like adding VM arguments or turning off my antivirus. None of this worked.