Mirroring Callisto Update Site
It is possible to make a local mirror of all Callisto update site with a little known command:
java -jar startup.jar -application org.eclipse.update.core.standaloneUpdate -command mirror -from http://download.eclipse.org/callisto/releases -to c:\eclipse-mirror -mirrorURL http://your.local.domain
Run this command from Eclipse install directory (i.e. where startup.jar is).
Replace "c:\eclipse-mirror" with the local directory where the update site contents will be copied to, and "http://your.local.domain" with a URL which will point to the directory you informed.
Of course you will need to install a local web server, like Apache HTTPD and configure it according the directory/URL you specified before.
This is useful for making available a full Callisto release to internal corporate users, for example, reducing the bandwidth normally used with dozens of users downloading the same bits from external Callisto sites.
This feature also can be used to mirror any Eclipse update site and it is documented in more details here.