I've been putting in the hours with my ancient copy of Adobe After Effects. My mistress in this affair has been lynda.com. But Lynda's $25 monthly fee shouldn't be a barrier to learning this amazing application. A wellspring of free AE tutorials are available across the web.
I'm also a fan of aetuts.com. They have some great looking tutorials. Many are a bit too complex for me, or require third-party plug-ins, but there are also some real gems for the beginners like how to create the JibJab effect.