I have Canon cameras and do a fair amount of backpacking. The replies you've received are very good.
The T2i is fine -- good image quality in a basic camera package. The 24-105 is an excellent lens, but probably not as a single lens on that camera. The 17-55 is also excellent, and provides a reasonable focal range, but you probably don't need the extra weight of an f/2.8 lens for landscape photography. I'd recommend taking a look at the new 15-85 lens. It's an EF-S lens made for the "crop" cameras, and has what I consider an ideal focal length range for a carry-around lens. It's also built very well -- much better than the older 17-85. It does have a variable aperture that's not very fast, but for landscape this is much less of a concern.
I'd also recommend looking at the 60D camera. For less than $1000 it's an excellent performer, with what I think is a better user interface than any of the Rebel series. Don't be put off by the tilt-and-swivel LCD monitor -- you may find it very useful when the camera is on a tripod, especially at lower angles. Using the Live View for composing and focusing on a tripod works very well, and the tilt/swivel LCD makes it even better. You'll get much more accurate focusing with Live View and the zoom function than most AF systems can provide. (I wish my big Canons had the t/s LCD. I do a lot of architectural photography on a tripod.)
Finally, do take a look at the Panasonic Micro 4/3 cameras. We have two of them, a G1 and a GF1, and I'm thinking hard about adding the brand new G3 body. These are fully featured SLR cameras with large sensors (much larger than p+s cameras, not quite the size of the sensor in the Rebel.) They have eliminated the mirror and replaced it with an excellent electronic viewfinder. Autofocus on the Panny m4/3 cameras is very good -- quick and accurate -- and of course the whole system is "live view" all the time, making careful framing and focus on a tripod quite simple. The major advantage of the m4/3 is the size and weight of the equipment -- with the standard 14-45 zoom, the G1 is half the size and weight of my Canon 40D with the 17-55. This makes a big difference when hiking or traveling, and we've almost completely switched to the m4/3 system for those pursuits. Panasonic also makes several excellent prime lenses, including the 20mm f/1.7 lens which is a wonderful all-purpose carry around wide-normal lens.