Here are some organizations dedicated to documentary makers and documentary communities.

The D-Word
Hands down, The D-Word is the most active and supportive documentary community available for documentary makers from newbies to professionals, and all enthusiasts in between.

European Documentary Network
The European Documentary Network supports documentary film and television makers through education and outreach, such as its financing guide and its co-production guide.

International Documentary Association
The International Documentary Association supports the documentary community through education, funding, and advocacy.