Festivals, especially accompanying your official selection. Bring lots of business cards.
48 Hour filmmaking challenges, where often networking is how you join a team (see the threads on member Wheatgrinder's recent experience with a 48 hour challenge). And they facilitate the networking by hosting pre-challenge meetups, matching teams with participants.
Auditions. If you have a project in mind, advertise auditions for not only cast but crew. That's how we did our last short...most of our usual crew were busy the only weekend we were able to make our film, so we auditioned for crew. Met a TON of filmmakers this way, collected a lot of resumes for future reference.