Free (mostly) tutorials around the web
General After Effects Knowledge
For general After Effects tutorials for beginners don’t ignore Adobe’s own video and written tutorials on After Effects. Their After Effects Help pages can be very informative to beginner and experience user alike (for example this page about speed).
Creative Cow is a very friendly place where professional and serious After Effects users will answer questions. I have gone there with questions dozens of times and never had to post my question because it had been asked before by someone else – so use the search function first to avoid duplicate questions.
A scripting resource for writing After Effects expressions can also be found at Dan Ebberts’ Motion Script. A side note: Dan Ebberts developed the original IK and Bezier IK expressions used in Duik, and he also contributes a lot to Creative Cow where his answers have solved my After Effects problems many times.
Another scripting resource is jjgifford.com.
Specifically About Animation
Daniel Gies has done some great work with After Effects and offers some detailed tutorials. Daniel Gies Vimeo page | E. D. Films (has tutorial section, both free and paid) | YouTube page (make sure you check out his tutorials there on lighting)
David Legion offers a nice set of puppet tutorials here. Although part of his puppet rig requires Mettle’s Free Form plugin and Mamo World’s Auto Lip Sync, you can still learn a lot from his tutorial series even if you don’t have those plugins. I used Auto Lip Sync on my Stickman Reads the News video and found the $39.99 it cost well worth the time it saved me from manually lip syncing his mouth.