Battle Jump (Unapproachable East 42) states that if I fall from 5-30' above my target, the attack is treated as a charge. Since I 'charge,' does this require a full-round action? If I can jump as a swift action, such as from the Sudden Leap maneuver, can I initiate a Battle Jump?
As far as I can tell, if you use Sudden Leap you can charge as a swift action. Fun times. Consider adding in Shadow Jaunt and the move action version of the same, so that you can now charge three times in a single round (once as a swift action, once as a move action, and once as a standard action).
If I also have the feat Headlong Rush (Races of Faerun 164), at what time must I declare I'm activating the ability to gain double damage on a charge? (I'm aware doubling a battle jump's double damage is a tripling.)
It's also here, by the way:
http://www.wizards.com/default.asp?x=dnd/ex/20030301aI'd say when you declare the action in the first place. It says you do it "instead of" a charge, so you don't declare a charge, you declare a headlong rush, and that acts like a charge except with specific differences (more AoOs, double damage).
Also, add Leap Attack if you're going to do all this, and don't forget the stance that adds 10' to all jumps.
JaronK