These two After Effects expressions are pretty simple, but they make slide show projects a breeze!! The first, "AutoZoom", makes a layer zoom (scale) based on the in and out points of the layer.The "zoom" value, is how much it zooms.  Positive or negative values will both work.

//AutoZoom - Apply to Scale

zoom = 10;
value + linear(time, inPoint, outPoint, 0, [zoom, zoom])

Next, AutoFade creates fades on head and tail of any clip.  The transition is specified in the "transition" variable, which is defined in frames.

//AutoFade - Apply to Opacity

transition = 20;       // transition time in frames
tSecs = transition / ( 1 / thisComp.frameDuration); // convert to seconds

linear(time, inPoint, inPoint + tSecs, 0, 100) - linear(time, outPoint - tSecs, outPoint, 0, 100)

Download both as FFX Presets

See a Demonstration Here (No Audio)