I received my RS-4 Camera strap in the mail today. This will become my strap of choice for casual shooting as well as for sports shooting (particularly when I've got the 300mm lens attached to a monopod with the 70-200mm lens slung over my shoulder attached to this strap). This is from a company called Black Rapid out of Seattle. It's a pretty cool rethinking of a better functioning camera strap.
Check out this video describing the strap and how it works.
This strap is now available at B&H Photo Video.
Amazon sells the older RS-1 version of this strap at the link below.
BLACKRAPID RS-1 Camera Sling Strap
You can order the latest RS-4 version of the strap directly from Black Rapid.
