I've been using the BlackRapid RS-1 camera strap for about a month. The idea is a camera strap allows you to carry the camera at your side at waist level. It runs up and down the strap so you can quickly grab it and use it. There is a video on the site that shows it off much better than I can describe it.
I'm a fan, but Scott Bourne from TWIP disagrees. He's had some bad experiences with it but I've never had any of these issues. Your mileage may vary.