MSN Encarta Article on the Celts	National Geographic's Multimedia Presentation on the Celtic Realm	BBC Online Welsh Language Programs
English Heritage Interactive Map of Stonehenge and Surroundings	English Heritage Interactive Map of Old Sarum	BBC Animation to Reconstructing Iron Age Roundhouses
English Heritage History of the Stonehenge and Surroundings	BBC Ages of Treasure Timeline and Game	BBC Archaeology Game Called Hunt the Ancestor
	BBC Animation of Iron Age Burial at Wetwang and Reconstruction of Chariot Found There

Where you thinking more in terms of courses? (please note, I have found these online, but have not tried them all out.  I cannot vouch for them personally)

The Gaelic College of Arts and Crafts has programs in several locations:
http://www.gaeliccollege.edu/index.html

This is a link to the Department of Welsh at the University of Wales, Lampeter.  They offer online courses and it looks like some online Masters:
http://welsh.lamp.ac.uk/Department/English/about/index.php

Online Non Credit Course on Celtic Music from the University of Wisconsin:
http://www.dcs.wisc.edu/LSA/online/celtic.htm