Floating Text: 
Well... lay down a trigger that you want the PC to cross. Then put a 
script in the OnEnter event of the trigger:

void main()
{
object oPC = GetEnteringObject();
int nDisplay = GetLocalInt(OBJECT_SELF, "do_once");
if (!nDisplay)
{
AssignCommand( oPC, ActionSpeakString( "I am displaying floaty text.", TALKVOLUME_TALK));
SetLocalInt(OBJECT_SELF, "do_once", 1);
}
}

Note that this will display the string only over the head of the first 
PC to enter the trigger.