*** Update Jan. 26 - 70mm tests have been uploaded.

This gallery is street comparison of several popular Canon L series lenses:
Canon 17-40L f/4 @ 24mm, 35mm at f/4 and f/8
Canon 24-105L IS f/4 @ 24mm, 35mm, 70mm at f/4 and f/8
Canon 24-70L f2.8 @ 24mm, 35mm, 70mm at f/4 f/8
Canon 35L f/1.4 @ 35mm at f/4 and f/8
Canon 70-200L f/4 non-IS @ 70mm at f/4 and f/8
Canon 28-135IS f/3.5-5.6 @ 35mm, 70mm at f/4 and f/8

The intention of this test was to help me decide what lenses I should upgrade. Though I felt the 17-40L was a keeper and I had no intention of replacing this UWA lens, I felt I may be able to improve mid range zoom by replacing the 28-135IS. I currently do not have a good long zoom, so testing the 70-200L would give me first hand experience with this beautiful lens.
As I was testing rental lenses, I did not have the opportunity to find an ideal location. I had to settle on shots right in front of the store during a lunch hour. Regardless, I learned a lot during this test.

Some notes on the test. All shots were taken with a Canon 5D, tripod mounted with the mirror locked up to avoid any camera shake that may affect the results. As much as possible I tried to take the exact same shot with each focal length, though it was tough because I had to bring the camera back into the store to exchange lenses (though the tripod stayed in the same location). All shots were taken within 45 minutes of eachother. I used the camera's centered weighted average metering and the autofocus was set to the top right autofocus point which was around the middle of the hotel in the 24mm pictures. I felt this would help ensure consistency.

All images were captured as raw files. No processing was done against them aside from the obvious cropping. They are represented exactly how the sensor captured them.

I realize this isn't much in the way of a scientific test. That said, I tried to reduce the number of variables that otherwise might affect the results. Because there are so many questions regarding the sharpness or quality of these lenses and how they compare to each other, I decided to post these images (and their 100% crops) to help others in the same boat as me. Please keep in mind that this is just one comparison on one day. Even if certain images stood out for you, consider doing a similar test yourself and above all, try the lenses on your camera to get a good feel for ergonomics. I hope you find this test of some value when it comes to making a decision on your next purchase.