Prefer learning with video? A few new things worth linking to:
First up is Learn OmniFocus. Tim Stringer started the site up right when OmniFocus 2 for Mac launched, but already has quite a few articles, video tutorials, and soon, live classes—all ready to go. (You can check out a lot of content for free, but access to all is behind a paid membership.)
And then there’s the Screencast Academy’s “Masterclass”. “OmniFocus 2 for Mac” is a 22-video course on nearly every aspect of the app. Even an intro-to-GTD® at the start.