You can download Commonclipse from the SourceForge Server . The zipped file includes both binaries and sources.
Unzip the downloaded zip file in your eclipse/plugins folder.
Releases > 1.0.x are for Eclipse 3.0 only. Get 1.0.1 if you are running Eclipse 2.
Online updates are available on http://commonclipse.sourceforge.net.
Define a site bookmark in Eclipse's Update Manager view (Eclipse 2.x), navigate to the update site via this bookmark and install the Commonclipse feature.
In eclipse 3 select "Help" -> "Software updates" -> "Find and Install" -> "Search for new features to install". Click "add update site" and insert the commonclipse update site URL.