Learn to Code: The Full Beginner's Guide

Learn to Code: The Full Beginner's Guide is 4.5-part intro series on Javascript from LifeHacker. It might be useful for using expressions in After Effects. And it doesn't leave you hanging since the epilogue shares some best pactices and additional resources.

Here's a sample movie:

SynthEyes Javascript export to After Effects tutorial

SynthEyes 2011 is out and offers tracking, set reconstruction, stabilization, and motion capture -- and there's free or discounted upgrades to users who purchased after June 2010. Among the many new features is a full-featured export to After Effects using Javascript, which supports textured Cards, moving objects, automated background setup, and SynthEyes-equivalent undistort and redistort layer effects inside AfterEffects.

Here's a quick tutorial on this from SynthEyesHQ (along with 5 others):