What editor to add audio to digital camera video?

I have a digital camera that records 640x480 movies w/o audio. I use an mp3 player/recorder to record audio for the scene and, during editing, manually line up an audio event with the correlating video event ( eg. knocking on a table). I’ve been doing this in Power Director but I’d like to know if there’s an easier way. I would like a system that allows me to make an index mark on the video/audio events and push a button to line them up and crop the audio ( which is longer than the video). Anyone know of an editor with this feature?