This “You Tube” video was first shown on the History Channel and is about the tunnels in Vietnam.
Although this is a US made video it has a lot about the Aussie involvement with interviews from members of 3Field Troop RAE.
It runs for 44 mins but is worth the time.
http://www.youtube.com/watch?v=Z4F5p_JJQH0&feature=relmfu