With starling v1.3 came the introduction of filters.

In this post i will show how to use the DropShadow filter.

the fiilter takes 6 Parameters: Distance, angle, colour, alpha, blur, resolution.

Make sure you download the latest version of starling and add it to your project  http://github.com/PrimaryFeather/Starling-Framework/zipball/v1.3

// import the filter

import starling.filters.BlurFilter;

//apply it to a starling object

starlingMc.filter = BlurFilter.createDropShadow(4,0.785,0x000000,0.5,0.3,0.6);

During my early tests i created a reusable filter var and applied it to all the required sprites. This caused a massive draw call increase and caused my the iPad3 to crap out.
After some investigation it was concluded you must not reuse a filter for multiple sprites, instead you must attach a new filter every time. Kind of goes against the DRY principle, but thats just the way it currently is.