Most cameras have a loop or two built into them for you to attach a carrying strap. My camera (a Canon Digital Rebel XSi) has them built on the top left and right of the camera body which often leaves the strap in my way, or worse, covering the lens. There are many after market straps you can buy to fix these problems. My favorite is the R-Strap by BlackRapid. There is one problem with this strap... it costs around $50. That's a little steep for a strip of fabric, a bolt, and two dog leash style hooks. Fortunately, all you need to make your own DIY R-Strap is a strip of fabric, a bolt, and two dog leash style hooks.

I got the idea to build my own strap from diyphotography.net's instructions. I got my strap off a cheap walmart camera bag. The rest I picked up at Lowes:
1. the shortest course theaded 1/4 inch bolt I could find
2. a small rubber washer
3. any metal strap that you can attach your strap you scavened off a cheapo camera bag. I used a strap made to hold flexible water tubing to a wall. All I had to do was drill a small hole in it.
Here it is attached to my camera.
One cool thing about this strap is that it is universal since it attaches to the camera using the standard tripod mount. You can even attach the strap to a simple point and shoot camera.
The utility of a strap like this on a camera that can you slip into your pocket is limited, but this picture shows the flexibility of this $5 DIY R-Strap.