Well, as a member you get monthly (more or less) issues of the national newsletter, the Fantasyline Express, which cantains stories about the club's national and chapter events and many things Disney (theme parks, movies, books, collecting, and others). You also have access to the members's section of the website, nffc.org, where we provide information about the club and upcoming events.
You can also attend the national organization's events, like the NFFC Convention hald in California every July and the Florida Convention, which is held at the end of September. The national club also hosts special events like a Disney cruise that's being held in May and a trip to New York to see the Disney Broadway shows (which is this fall, IIRC).
As a member, you can also join local chapters of the NFFC; as trypnotic mentioned, it's a great chance to get together with your fellow Disney fans and do a lot of fun things! For example, I'm in the Los Angeles chapter, and we hold monthly meetings where we've had guests like Dave Smith and Robert Tieman from the Disney Archives, author David Koenig, and artists Terri Hardin and Dave Avanzino. We've done group trips to visit sites related to Walt Disney in the Los Angeles area, Walt Disney Concert Hall, Walt's Barn (the barn that used to be at his home that he ran his backyard railroad from), the El Capitan Theater, and of course Disneyland. We've also had members put on presentations about about things like their trips to the Disney parks and Disney music. Obviously not every local chapter can get speakers or do trips to a theme park as part of their chapter meetings, but I've been pretty impressed by what they can do!
Work is what I do between Disney theme park visits.