Originally Posted by vachss
To the OP I'd ask what problem are you trying to solve? L lenses can be the right choice for some things, EF-S lenses for others and manual focus primes for still others. For high quality general purpose use I'd recommend the EF-S 17-55, for shooting in a war zone or inclement weather I'd recommend the 24-70 (and a 1-series body), for low light and shallow DOF subjects nothing beats fast primes.
The 17-55 F2.8 is probably the best EF-S lens. As far as optics goes, I can see little difference between it and the 24-70L. Build quality is as good as a non-L gets, but it doesn't have the weather proofing of the L, which happens to be a nice piece of mind when shooting.
I've owned the 17-40mm and traded it off within 1 week of purchase because i didn't like how much distortion the lens had. I ended up with the 16-35mm F2.8L which has miles less distortion and benefits from being 1 stop faster when wide open. That being said, people love their 10-22mm EF-S lenses, the only part I couldn't deal with on that lens is that it isn't a constant F stop. Which as a result can cause it to not be as easy to use indoors or in lower light depending on your focal length.
The 24-105mm F4 is a fantastic lens. It is basically as sharp as the 24-70 F2.8, but it lacks the extra aperture. And to some that can make or break. However, the addition of image stabilizer tips the scales in it's favour as well.
In my personal opinion, your choices should be between the 17-55mm F2.8 EF-S lens, and the 24-70mm F2.8L or the 24-105mm F4.
Keep in mind however, that 24mm will shoot more like 35mm on a crop body camera, so it might be worth considering one of those two with a wider angle lens as well to make up for some of that lost wide angle focal length.