Recommend headphone amplifier
 

Needs to boost the signal, and here's the tricky part, route one of the channels to both ear cups. Basically, I don't want to hear one of the channels at all, and I want to hear the other channel in both ears. Signal is coming from the headphone jack on a camcorder.

Does the headphone amp have to be battery powered?
I would use a Mini-TRS male to 2x TS 1/4" male Y-cable, then plug in just the appropriate one of those outputs to any number of available devices that can give you a boosted mono headphone feed.
Are the line outs of the camera already in use? That could give you an easier solution.

Yeah, it has to be battery powered. I'd rather not use the line outs, because that means dealing with another cable. I'm using a beta-breakaway cable and don't want another wire.

I don't know of a specific headphone amp with internal battery power that will do precisely what you want. There are a number of combinations of equipment and adapter cables that will do it, but it would depend on what you wanted to carry around.

Think I got it
 

I was reading in the manual of my SD302 and its says that there is a menu setting that will sum both channels and give you a mono mix of the return feed. So, what would be the best way to feed it one channel? Can I just get a small extension cord and snip one of the wires? The return feed has a stereo miniplug input.

You could use a mini-TRS to mini-TRS cable and snip one of the main conductors as you suggested. Or you could use a right-angle mini-TRS male to 2x male RCA cable and the following adapter with the wrong name in the title from Radio Shack:
http://www.radioshack.com/product/in...entPage=search

Then connect only one of the RCA ends of the Y cable to the adapter. You wouldn't have to snip anything or change any menu settings. You could also change which channel you listen to as well as have the other channel available for some other purpose.

Perfect thanks!