Rowan Williams gave a Presidential Address. For an html copy of the full text it is necessary to go to ENS who have kindly reformatted it here.
The official press release about it is here.
ACNS has however the full text of the Sermon given by the Right Reverend Duleep de Chickera, the Bishop of Colombo at the opening service in Canterbury Cathedral.
The Order of Service is available as a PDF here.