You can create your own scripts in a couple of different ways.
(actions are easier to record than writing scripts, but one needs the full version of photoshop such as photoshop cs6 or cc2014 to record the actions)
Java script is the most common, since it's works on both mac and windows.
(not to be confused with java script for internet browsers and such)
You can write your own or it's possible someone else has already written one.
As far as actions go , by far the easiest way is to use the full version of photoshop to record an action.
(pse 11 can load and play actions recorded in photoshop, but doesn't have a built in action recorder)
It's probably much easier to find an action already made than a script.
What kind of script or action did you have in mind?