We had a situation come up tonight in a game that caused some disagreement.
The situation was a PC who was prone 15' from an enemy. He wanted to stand (move action), then bull rush the enemy.
My opinion was that a bull rush (unless made as part of a charge) could only be made against a foe you threaten to start with. Since the PC didn't have enough actions to stand, move to the foe and then attack, nor could he stand and charge, I said that a bull rush was not possible.
The opposing view was that bull rushing inherently involves movement, and so the PC would be able to move and bull rush as part of a single standard action after using a move action to stand.