Word Play – One of the best resources for screenwriters online – extensive articles from Ted and Terry (Pirates of the Caribbean, Shrek)
Mystery Man On Film – One of the power bloggers in the screenwriting niche – Mystery Man’s work can also be found in Creative Screenwriter and Script Magazine.
Unknown Screenwriter – Great posts and great resources in the scribosphere section of the sidebar.
Go Into the Story – A regularly updated blog from Executive Producer of Distillery Pictures and screenwriting professor at UCLA.
Screenwriter’s Utopia – An extensive resource for just about all your needs as a screenwriter