BBC:
State of the Planet
Lost Cities of the Ancient
Day that shook the world Vol. 1 & 2
Earth Story
All those WWII documentaries from BBC
all those Discovery DVDs from Magnavision
Most Astrovision has a section reserved for documentaries. Go to one located in one of the more fashionable mall (ie Trinoma, MOA, Megamall, Robinsons Place Manila, etc), they tend to have a better selection than malls where there is less foot traffic.