CustomSLR's Glide Strap ($35.95 for the strap and $64.95 for a combo with the C-Loop Camera Strap Mount) is a very comfortable, generally well-designed sling strap that's worth the money over the typical cheap neck strap that comes bundled with most cameras.
The highly modular architecture involves several components: a clever neoprene shoulder pad (the Glide Strap with Split Strap technology) with a gap in the middle and quick-release rotating endcaps to better mold itself to your body; 70 inches of slick-textured webbing; a plastic connector that slides along the strap plus a single cam buckle to act as a stop; and a pair of small straps that attach the connector to the C-Loop camera mount.
My favorite part of the system -- the part that I have zero problems with -- is the C-Loop, which has a very clever and attractive design. It stands out over BlackRapid's Sport Slim attachment in two notable ways: it has a little handle that makes it easier to screw in (which gives it an edge over Sun-Sniper's Strap-Surfer design as well) and it's flat-bottomed so that you can more easily perch the camera to stabilize it when shooting video or at slow shutter speeds.
Discuss Custom SLR Glide Strap