I want to animate things growing or shrinking in size. I swear I did this before, but can't figure out how I did it. Maybe I'm just dreaming and Ps CS3 Extended doesn't have the ability to do this, but I thought I did it, and it seems so elementary and useful for the types of things they always show off the animation feature with (ie painting or cloning our a logo, etc). I just can't figure out how to do it. I just want to set the size of a layer, then have it smaller a few frames later so Ps can tween the shrinking motion. Can it do this? If so, how?
Unfortunately Photoshop does not have the ability to animate scale via interpolation.
You could possibly fake it using a Pattern and animating the Style.
Another option is to use a blank video layer and clone across frames. You can set the frame offset and scale of the clone source so that it will clone from the previous frame at a reduced scale. If you use a big enough hard brush could possibly just apply a single click to get all you want cloned. This is how the spinning wheel things in the sample file CheeziPuffs.mov was done. (starts around 10 second mark)