I finally bit the DSLR bullet and bought a Canon XSi with a 18-200 zoom lens to replace my large-ish point and shoot. Does anyone have a tip how to protect it in the backpack without adding a lot of bulk and weight? Most camera bags like the Crumpler and Lowes are a not something that I want to add to my load. I also really don't want to wear it round my neck most of the time, and just wrapping it in some clothing is a bit impractical and probably not too effective.

I know, not exactly lightweight, but it takes really nice pictures.

Why do you want your camera inside your pack? You will miss a lot of photo opportunities that way. I like mine where I can grab it quickly. I understand the part about not hanging around your neck. I hate the way they swing around while you are walking. A holster style or a chest harness might be an option.

Check into something called "Camera Armor" - http://www.cameraarmor.us/ .
I agree, you need to keep the camera where you can reach it so that you can use it for what you brought it along for. For me (I'm technically a professional photographer), the camera isn't that heavy, it's the lenses that are heaviest. While I don't use the camera armor, I do keep my camera strapped over my shoulder and all my extra lenses are in a small bag either strapped to the top of my pack or at the top on the inside (depending on how much food and gear I have on the trip).

Scott:

Have you used it? Reading reviews on some of the retailers' sites, a few users haven't cared much for that silicone acting like a "dust magnet."''

Thanks Scott, Camera Armor might just be what I'm looking for. I'll order some and see if it works. Back in the film era, almost every SLR came with a small, thin leather case that worked beautifully, but with all the buttons and the LCD displays, it doesn't really work anymore. I still love the Zeiss Ikon cases my grandfathers 35mm SLRs came in. Light, tough, non-bulky and the acquired a beautiful patina over the years.

Regarding the in-your-backpack vs. neck strap issue. I can see both sides, but for the last 20 years, I always kept my cameras in either my day pack or my backpack. It might be a bit slower, but with practice, I can get it out and take a picture in a few seconds. I've done it so often that it is pretty much automatic and I can't remember any shots I missed in years:

-unclip hip belt (if it's not the daypack) and slide out of the right shoulder strap
-swing pack forward on the left shoulder strap
-unzip with the right hand
-slide hand through the wrist strap or hand grip
-take out camera

If it looks like there are multiple opportunities, I just carry the camera on a neoprene wrist strap.

There are a few reasons why I do it this way. For once, I often travel and hike in countries where my camera is worth a few months wages. Secondly, wearing a 3 pound camera on a neck strap hurts my back fairly quickly. Also, people are very often more open if you don't have your camera out right from the beginning. On the wrist strap or hand grip, I can also wear it low on my side, so it's not that noticeable. Obviously, that's more for street photography than for backpacking.

The other issue is that I don't like a few free swinging pounds on my upper body. I once screwed up my knee pretty badly when a bag I was carrying shifted at exactly the wrong time while scrambling up a mesa. (I know, I was an idiot for carrying it in the first place.)

YMMY, obviously.

I know what you mean about the fitted leather cases. I still have one along with my Minolta XD11 that I purchased in 1978. Since moving to a DSLR, 6 years ago, I have been frustrated with the lack of these as well.

I used this while hiking and rafting in the Grand Canyon. I reduced my camera down to a Canon G9 for that trip, and carried it in a very small Tamarac case on the harness. I also used the harness for the camera in it's waterproof housing for rafting and floating down the river. The camera in the housing is about the same size as a DSLR with a medium zoom lens. While hiking, I put the harnes on first, then the backpack over it. I was very pleased with it.