I heard an interesting story about those winglets that you see on the planes.
Specifically the Aviation Partners Boeing blended winglets seen retrofitted to the 737, 757, and 767. The newest 777s, 747-8, and 787 use a raked wingtip developed by Boeing themselves (AFAIK) which is even more efficient for long haul.
The next generation of 737s (737 MAX) are going to use a scimitar winglet, also developed by APB.
True story: Boeing's first jetliner with winglets was the 747-400 in 1989 and they were done for marketing--they didn't really reduce fuel consumption hardly anything past the additional drag and weight of the winglets themselves.