I just take a quick check over my shoulder to make sure that there aren't any cars close behind me and I move out into the lane to let them pass inside. I figure its safer that way, cars somewhat expect a cyclist going with traffic to move into the lane more than they would someone riding straight at them, plus its probably safer for the wrong way rider to be closer to the curb, if that makes sense... Sometimes the wrong way rider takes the lane to let me keep my course before I let him, either way as long as both of us see each other it's no big deal.

Personally, I don't have any qualms with riding into traffic for short stints as there's usually enough room on the side of the road but when I happen to pass another cyclist going the right way I feel like a pretty big d-bag. Like I said though, as long as you both see each other it's usually not a big deal to get around.