I have definite preferences when it comes to what kind of documentaries I like most. They're short, well written, and more often than not have something to do with people in a far off land I've never been too (even if that place is in the US!). They all teach me something I didn't already know. I also like the fact that many of these could easily be a spot on any news program. It's interesting how really good news journalism can be exactly like many short docs.
I love Current TV. This doc is on cave dwellers in China. It's amazing to think that people actually live like this these days! Just add this to the places in the world I need to visit.