A great time-saving preset to "duck"(fade in/out) a music layer based on a voice over.
"Ducking - Audio Terms Explained - Process of automatic compression, eg when the announcer's voice signal causes the level of music to be attenuated."(from lp2cd.com)

If you want to use the speed/velocity of a layer's movement to drive an effect ...

Once you run the animation assistant for Exponential Scale, the keyframes are locked down and if you need to change the start or end values, you have to delete all the intermediate keframes and re-run the animation assistant. Here is a way to replicate the Exponential Scale via expression.

If you want a property to animate on 2's or 4's like they do in cel animation.

Here is an expression for having a marker trigger a squish and squash. Put the expression on Scale.

A simple utility that copies the current composition image to the System Clipboard, allowing easy pasting into other image applications (such as Photoshop). It bypasses the task of saving the current frame to an image file and then reopening.

This will make your layer/object bounce along an imaginary 'floor'. Paste it into the 'position' attribute for your layer.

found at CreativeCow