Update September 2009: see also addresses for eclipse 3.6 Helios
For eclipse itself, the eclipse wiki
However, the Milestone names are not there yet.
(For instance, the build number there is 20080807 is assumed to be 3.5M1)
The update site will be added as a location for builds in order to get published to automatically:
see bug 248509
Warning: the update process in itself might generate some freeze (see bug 234916) which might be solved by using a local http client (bug 220240).
Meaning you should first update your eclipse installation with the ECF_Apache_Httpclient-Based_Provider update site (http://download.eclipse.org/technology/ecf/httpclientrepo), then try the different update sites mentionned for eclipse components.
Update May 2009
The page "compare package" now provides all links to different released packages
(See links to the left of the page: Europa 3.3, Ganymede 3.4, Ganymede SR1, and Galileo 3.5Mx)
The current available Galileo M6 lists packages built with M6 release. That address will soon be not valid since Galileo M7 has just been published (May, 2d 2009).
The new Galileo packages (M7) will then be at this address.