Some useful links for an audiovisual celebration of the Advent and Christmas online:
BBC Online - surely the best English language information resource on the net - has areas in its Religion and Ethics section related to Advent and, in particular, Christmas. There are clips, both audio and video, of carols online.
From WBUR in Boston: "For its 50th anniversary, the early music group Boston Camerata teamed up with several Arabic musicians to recreate Christian music from the Middle Ages. They've used medieval texts and illustrations, and arranged music played by Christians, Muslims and Jews, exploring musical traditions that merged religions and cultures." (Real Audio)
See also the ABC's Religion and Ethics website, but they don't seem to have anything particularly special for Christmas.