One-sided layers

//found on :http://www.mographwiki.net/After_Effects_expressions_library

Apply this expression to the opacity attribute and it'll disappear 
whenever it's flipped away from the camera. You need to have an active 
camera in your composition for this one to work.
 

a = toWorldVec([0,0,1]);
b = thisComp.activeCamera.position - toWorld(anchorPoint);
c = dot(a,b)/length(b);
if (c > 0) 0 else value

Bouncy Scale In

 //found on : http://www.mographwiki.net/After_Effects_expressions_library

Apply this expression to the 'scale' parameter of your layer.

k=100; // final scale
a=5; // how quickly the bounce ends
b=20; // how many bounces it'll do (that is, the bounce speed)
x=k*(1-Math.exp(-a*time)*Math.cos(b*time));
[x,x]