I carry a chunky SLR. When I'm hiking, I usually have it around my neck and cradled in my hand. A good chunk of my activity in the outdoors is taking shots. I'm pretty much always on the look out for interesting compositions and will typically snap about 200 shots off or so in a day. Of course usually only about 20 are ever actually saved and edited during post processing.
For the most part, SLR's are built to be pretty rugged against the elements. My nikon has been through a lot of light rain without any hickups. I will stick it in my jacket periodically to keep it from getting drenched, but I hate doing that as it invariably fogs up the lens. I keep a clear UV filter on the lens at all times to keep the actual lens from getting scratched. When I'm walking around on my hikes, the lens cap is almost always off (in my shirt pocket or the camera bag), the camera is on and in my hands ready to take a shot. Sometimes you get a problem with fogging between the filter and lens when you switch in an out of humid environments. You have to unscrew the filter for a few seconds to demist the lens.
I have a Zoom SLR camera bag that is pretty compact and just fits my body + 18-200mm lens. I used to keep my camera in a pelican case and I grew way to tired lugging that thing around. The camera bag is padded and overs pretty decent protection from the elements. It can be threaded through my belt, but I usually just clip it via a couple of carbiners to my bag. I carry a small dry sac in my back pack that the SLR and camera bag can go into if the going gets really nasty or if I'm canoeing and such. Haven't had to use the dry sack yet.
A little tripod is useful to carry with you too.
When I bought my first SLR I was all anal about protecting it. Now, having gone through a few different bodies I am a lot less careful and just use the camera and don't really worry about it too much. Again, if it is a tool you are always using then the best protection for it is having it be actually used. Kind of like eyeglasses. Its the guys who are always taking them off that keep losing and breaking them. The guys who leave them on their face keep them in good shape.