There should be a link to the FC4t1 release notes on the front Fedora project
page. The notes are currently on the Fedora project wiki at:

http://fedoraproject.org/wiki/FedoraDocs_2fRelNotes_2fCore4Test1RelNotes

During the testing period, a link should be very prominent on
http://fedora.redhat.com -- and possibly even on http://fedora.redhat.com/docs/
-- to direct people to the interim release notes.

Note that on the front Fedora project page, there is already a link labeled
"Release Notes" that redirects to:
   http://fedora.redhat.com/docs/release-notes/
That page only leads to release notes for final releases (FC2+3), but it seems
to me there's no reason not to put FC4t[123] here during the test phase.