See http://www.eclipse.org/callisto/
The following links are just reminders for those contributing to the Callisto Discovery site.
Minimum starting platform: Platform Runtime Binary M0609
Callisto Coordinated Update Sites
Callisto Simultaneous Release Plan
For most distributions of Eclipse, there should already be a "Callisto Discovery Site" defined in its Update Manager. But, if you do not see it you can try adding the following URL as a remote update site in your update manager.
http://download.eclipse.org/callisto/releases/
Alternatively, if you would like to view the list or projects by their Eclipse Project (PMC) organization, you can define a new remote update site, and specify a site-byProject.xml file. In other words,
http://download.eclipse.org/callisto/releases/site-byProject.xml
See Eclipse Help for general information about using Update Manager.