Intimidating Strike (PHB II, p 79) is Demoralizing on crack.
Basically, you subtract a number from your attack roll, ala power attack. If you attack hits you get to make an intimidation check with the penalty you took on the attack roll as a bonus. If that works, the opponent is shaken for the rest of the encounter. Now, you can't improve on already shaken foe with this, but with someone that is shaken already is easy to improve on. This only works with a standard attack so you can't combine with a full attack or with maneuvers, but it's pretty easy to dish out damage with a single attack.
Daunting Presence (LM, p 25) allows a standard action to awe (read: render shaken) a single opponent for 10 minutes if they fail a will save (DC 10 + 1/2 Char level + Cha Mod). Again, this stops at shaken.