I am trying to take a shape (a rectangle stretched edge to edge across a document) and make it ragged looking, with torn edges, etc. Any ideas on how to pull this look off effectively?
#1
tear some paper and scan it sounds easiest...
rule #1. don't make things harder than they need to be! :)
#2
Check MyJanee.com, she has a nice simple tutorial.
Not everyone with Photoshop has access to a scanner, Dave. Involving any additional hardware or software beyond PS could be considered "making it harder than it needs to be!"
#3
There is a plug-in called Splat" from Alien Skin.
This will several different styles. I think there is a free demo online for download.
#4