If you happen to own an ocean freight liner...

...this looks like a really cool idea. Stick a massive kite onto it, hook up a super-high-tech automated control system, and watch your fuel usage drop by 50%. If you're as geeky as me and want to find out more information, there's some here and a video link at the bottom of this page (haven't looked at it myself yet since I'm on dial-up at home).