A photography and filming crew from National Geographic Channel joined the team in 2010 on a 20 day expedition into Hang Son Doong ("Mountain River Cave").
Together with an international team of scientists they hiked deep into the jungle of the Phong Nha-Ke Bang National Park and descened into the abyss to find out the thruth: Is this cave really bigger then Deer Cave (Malaysia), the current record holder?
You can read the report of the expedion in the January 2011 edition of the National Geographic Magazine both in paper version as well as online. On the NGC website you can also find a nice picture gallery and an interactive map of Hang Son Doong.
The documentary "World's biggest cave" will be aired the first time in Europe on January 30th at 21.00 (GMT+1). You can find the trailer below:
Update 1 (10/01/2011): It seems there is a lot of controverse about the claim (see for instance on Mulucaves), not really about the dimensions they measured, but about the definition of 'biggest cave passage'. As long as there are no definite rules about what should and what shouldn't be included there will allways be dispute. Compare them for yourself:
Update 2: (10/01/2011): Howard Limbert published all expedition reports and surveys online: you can find the survey for Hang Son Doong here and and overview of the Ke Bang caves here.
Update 3: 12/01/2011: You can watch the complete movie here: