If you smell it - there is a leak. It's probably just really small right now and hard to find.

A few people have had problems with leaks that leak onto the manifold - so it burns off and you never see anything on the ground.

Polish up your detective hat and be persistent

I had a post-drive smell recently that turned out to be a clamp that wasn't quite tight enough on my upper radiator hose. My power steering hose clamps just gave out as well. It's not a bad idea to just start systematically replacing all the crappy factory clamps (especially the stupid spring-tension ones that don't even have a screw to tighten them) with the old-school screw type.

ETA - there is also a TSB somewhere about coolant smell - there is some gasket in the thermostat area that goes bad on some vehicles... anyone know what the hell I'm talking about?