There are many websites and email lists that you can read for more information on Firefly and Serenity. A select few are listed below, but you’ll find Firefly everywhere!

Join the New England Browncoats!
http://tv.groups.yahoo.com/group/NE_Browncoats/

The Original Board (OB) is the official discussion board that was set up by Fox when Firefly was originally being broadcast. It’s still in existence and as lively as ever. Look for Adam Baldwin posting in the political threads!
http://forums.prospero.com/foxfirefly

FireflyFans.net is one of the oldest fan-run discussion boards around.
http://www.fireflyfans.net/

SerenityMovie.org hosts the discussion boards that were originally set up by Universal to promote Serenity.
http://www.serenitymovie.org/

Whedonesque is a website to discuss all things Joss Whedon. Joss himself posts there from time to time.
http://whedonesque.com