Upload & Sell: Off
The Canon CPS strap is pretty sweet. (now THATS a joke )
I've been very happy with the Black Rapid RS7. I've carried it all day many times with my old D90, 17-55 and 70-300 without any problem. And I use it now with a 1D and 24-70 2.8. Never had any shoulder or neck pain from it, and I like that it's fast to move around and take off. It's a little expensive though, but I've seen some sell for $25-$30 on the B&S here.
I was previously quite happy with one of these. A friend of mine still uses one on his D700, but with your D3 being even heavier, I'm not sure I'd go that route. If you find one in a local store, I'd check it out though. It did feel really good around the neck and over the shoulder.