there are hundreads of tutorials online for aftereffects, just google things you want to learn to do and someone probably has the info on it.
There are also TONS of plugins you can purchase for aftereffects that are really mind blowing. Most of the cool effects you see people like digital kitchen or motion theory doing are plugin based.
This tutorial site is new, but its sistersites for photoshop and the liek are amazing, so im sure it will be a great resource in the future.
After Effects Tutorials - AETUTS