Hey. I was looking for a mod that makes certain skills decrease when you don't use them. For example, if it has been a month and you haven't used your sword at all, the mod would make your long blade skill decrease by a certain amount.

This might do it:
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=2699

Going to jail decreases your skills, so if it's not hard-coded, you could look into the script that governs that function.

I can vouch for Balor's Leveling. I've used it since 2002. It's in my short list of must-have mods for every game.