I absolutely HATED the stock Nikon D80/D90 strap, and looked around and found this Tamrac N-25 ($20) at Adorama:
N2501 Tamrac N-25 - Shock Absorber, Neoprene Camera Strap-Quick Release - Black
It's neoprene (like wetsuit material) and is really comfortable on your neck/shoulder for long periods of time.
Here's a review of the strap:
Camera Straps