Check the following links:
Discovery Channel
http://military.discovery.com/battles-history/videos/world-war-1-videos.htm
BBC
http://www.bbc.co.uk/history/interactive/animations/wwone_movies/index_embed.shtml
Poster Art
http://www.pbs.org/wgbh/amex/wilson/gallery/posters.html
http://www.loc.gov/pictures/collection/wwipos/
http://pw20c.mcmaster.ca/case-study/british-first-world-war-recruiting-posters
http://digital.library.mcgill.ca/warposters/search/searchresult.php - the Canadian collection of war posters
Audio and Video are available from: http://www.firstworldwar.com/audio/index.htm
Discovery Channel
http://military.discovery.com/battles-history/videos/world-war-1-videos.htm
BBC
http://www.bbc.co.uk/history/interactive/animations/wwone_movies/index_embed.shtml
Poster Art
http://www.pbs.org/wgbh/amex/wilson/gallery/posters.html
http://www.loc.gov/pictures/collection/wwipos/
http://pw20c.mcmaster.ca/case-study/british-first-world-war-recruiting-posters
http://digital.library.mcgill.ca/warposters/search/searchresult.php - the Canadian collection of war posters
Audio and Video are available from: http://www.firstworldwar.com/audio/index.htm