Possibly the most important thing a new (or established) filmmaker needs is a community. Like-minded creators can help with issues during production, share contacts, give specific financing and distribution advice, commiserate and even go to your screenings when the film is finished.

Shooting People – a great, international group for networking with independent filmmakers
The D-Word – A large, international community of documentary filmmakers with a comprehensive forum-based resources
Massify – connect with other crew and talent, make films and content
LinkedIn – in addition to general networking, LinkedIn offers specialized groups for filmmaking, digital marketing, documentary, etc. Offers contests with fairly substantial prizes and a community video sharing site
CineSud – Latin American alternative distribution network