I think AE needs more than one source, because it is quite complex in itself, not to mention when you add 3rd party plugins.
I would start here on the COW – plenty of tutorial for basic stuff and more complex ones. Adobe is also a good place to get basic information. For more advanced tutorials, aetuts+, videocopilot and the 3rd party plugin sites. This should get you started.
Tudor “Ted” Jelescu
Senior VFX Artist