Black Rapid Sport
The black rapid sport is a fantastic camera strap. I tried Canon's factory strap for one day and immediately searched for another option. This strap fits comfortably and makes the camera feel like a part of me rather than like there is something weighing down my neck.
There is a Black Rapid Sport 2 version, same quality thinner strap, although the original was by no means unfashionably wide. If you have decently wide shoulders, I'd recommend the original sport.
CustomSLR Pro Dot Shutter Button Upgrade
The Pro Dot by CustomSLR is must have. Without it my finger curls into an uncomfortable, and unnatural hook that strains my finger. A feature that CustomSLR touts is how it reduces vibration as you press the shutter, and that my be true, but I simply love it for extending the height of the shutter button so my finger is at a more natural position. (Perhaps a full body camera without this accessory might feel more comfortable in my hands.)