There are many sites which deal with Aberfan disaster. A Google search will give you a good start. These are the links I have found the most helpful in my research.
The Aberfan Disaster – This is by far the best and most comprehensive. Written by Iain McLean and Martin Johnes of Nuffield College, Oxford, the site points to sources of further information
The BBC has a wealth of information. Simply put Aberfan into their search engine.
British Pathe News has a number of newsreel clips about the disaster.
The Wikipedia entry for Aberfan is useful but has many broken links in its sources section.
The South Wales Police Museum gives an account from the perspective of the police.
The Old Merthyr Tydfil site has excellent photographs and has some first-hand accounts.
Brian Lamb produced a helpful site Aberfan Remembered with poems and other material
Iain McLean has written on the 40th anniversary of the disaster with some excellent conclusions – Aberfan: No end of a lesson
Dr David Wright has written a moving account of the disaster.
Aberfan: The Terrible Price is a documentary DVD price £5.99 from Six-T media
The full text of the official report into the disaster “Report of the tribunal appointed to inquire into the disaster at Aberfan on October 21st, 1966″ can be found on the Durham Mining Museum site.