Top #1 - thermo nuke fusion for clean, free electrical energy. Not cold fusion, but real tokamak magnetic bottle or big laser inertial confinement reported here recently. Hydrogen is the most abundant element in the universe while the fossil fuels are running out. We'll never be able to support ourselves in the manner to which we'd like to become accustomed (much less lift most of humanity off the planet when the sun burns out) without an abundant energy supply. Shorter term, we'll be driving rechargeable cars (plug-in) and warming our homes on the waste heat of our personal datacenters.

You are absolutely right - it depends. In general, a sailing vessel's polar diagram predicts the fastest point of sail for any given wind speed. For example, with 8 knots of breeze, a Catalina 34 is fastest with the wind 60 degrees off the bow, but in a 20 knot blow she's fastest at 75 degrees apparent. While other boats will vary, iceboats are an extreme example, traveling so fast as to shift the apparent wind forward even when heading "down wind." I'm not sure how applicable any of this is to the kite-powered tanker. I was unimpressed by the video - the kite expended much of it's energy going side to side. Even when mostly ahead, the angle was so high as to exert more of a vertical lifting vector than forward thrust. But any little bit helps, I suppose, especially when you can take you time crossing large expanses of water.