You can also check out the Canon Forums on fredmiranda (http://www.fredmiranda.com/forum/board/2) and dpreview (http://www.dpreview.com/products/canon/lenses -- click on a lens and then click on the "User images" tab). You can also do searches on photo sites, such as flickr.
The Tamron website offers a focal length comparison tool that covers 10-500mm. Tools like that can be helpful, but also difficult to relate to scenes with which you are familiar. Another approach is to plug some numbers into Bob Atkins' FoV calculator (scroll down), to give you an idea of the area framed by a given focal length at a given distance (e.g. with a 10mm lens on 1.6x sensor, at a distance of 16 feet you frame a 36 x 24 foot area - that's about the size of a small, 2-story house).