AlarTTFrame adds a mini castbar to Target frame (12 buttons totally independent from standard buttons), and 4 new unit frame (Target of target, Target of Target of Target, Focus, Target of Pet), each one with a castbar.
To set castbars type /att spells, then drag and drop spells from your spellbook.
You can have different spell for different stances/forms (if u are a druid or a warrior or even a rogue)
You can differentiate between spells for friendly targets and spells for hostile target.
The target's minicastbar also shows the target's class (nice for pvp)
/att help
/att spells
/att gui