International Documentary Association (IDA) - The heavy-weight champion of all-things documentary. The IDA is a tireless advocate for documentary filmmakers. Founded in 1982, the IDA is a 501(c)3 non-profit organization that provides countless resources for filmmakers including educational seminars, fiscal sponsorship, funding opportunities and updated industry news to help filmmakers stay ahead of the curve.
the gotham (formerly IFP) - Founded in 1979, the gotham is the largest and oldest not-for-profit dedicated to independent film. Fosters the development, production and promotion of hundreds of feature and documentary films a year. Connects artists with essential resources at all stages of development and distribution.
The D-Word - A fantastic "meeting place" for documentary filmmakers around the world to discuss any and all topics related to making documentaries. This is a free forum and covers a wide variety of topics, everything from fundraising to distribution. They do require a sign-up process to access the "documentary professionals" discussions.
Docs In Progress - Although Docs in Progress is based in Maryland (near Washington, DC), this is still a great resource no matter where you're located. Resources include interviews with industry experts, funding opportunities, one-on-one consulting, summer youth camp and hands-on filmmaking workshops.
Desktop Documentaries - Of course we must include Desktop Documentaries! Includes 1000+ pages of free DIY articles, tips & resources for the independent documentary filmmaker. Geared especially for first time documentary filmmakers, includes a broad range of articles, courses and inspiration.
The Film Collaborative - If you've completed your film or getting close to it, check out the Film Collaborative for help on how to best distribute your film and find an audience. Download a free copy of "Selling Your Film Outside the U.S.", the second volume in their "Selling Your Film" distribution case study book series.
B&H Photo, Video, and Pro Audio - For production gear (cameras, mics, lighting, tripods, audio, etc), B&H Photo is THE place to go.
Creative Cow - Although this isn't a documentary specific site, this is a fantastic resource for all-things video production. A lot of video/film professionals hang out on this site and you can get some really good answers to your filmmaking questions here.
Documentors - If you're looking for one-on-one expert guidance, this is a great place to go. Husband and wife documentary team Hank Rogerson and Jilann Spitzmiller run this site as an extension of their production company Philomath Films. They have some excellent in-depth tutorials such as their popular Documentary Budgeting System offered exclusively here on Desktop Documentaries.
Videomaker - And last but certainly not least is Videomaker Magazine. Started in 1986 right after the release of the first personal camcorders, Videomaker is a vast resource for video professionals and video hobbyists covering everything you can think of involved in the filmmaking process including pre-production, post-production, equipment reviews, product comparisons, duplication, webinars, workshops and everything in between.