While surfing my catalogue of photos using Adobe's Lightroom, I had a look at my most popular lens. It turns out to be Canon's EF-S 10-22mm f/3.5-4.5 USM lens. It's responsible for around 30% of all my DSLR photography and I have around 10 lenses to choose from these days. So why is it so popular? Well Interestingly enough, this just happens to be my very first lens purchase for a DSLR camera. I also lack a standard zoom for a DSLR camera and therefore have to choose between a wide zoom or a long zoom lens. The long zoom happens to be my second most popular lens. I guess I prefer the wide end.
So what's a good subject for this lens. Well, looking through my collection again, I see that about 20% of my photographs belong to the landscape genre and about the same belong to the architecture genre. Two very good uses for such a lens. Here are some more examples from my collection.
The most obvious use for a wide angle lens is, to wind it back and get more into an image. Just like I did here. With such a wide lens there's no need to stop down to f/22 to get everything in sharp focus. At 10mm and f/7.1, the hyperfocal distance is only 75cm away.
The Thar Desert, Rajasthan - India

Canon Kiss Digital X with a Canon EF-S 10-22mm f/3.5-4.5 USM at 16mm EFL. Exposure Trio: 1/125s, f/7.1 & ISO 100.
Another great use for such a wide lens is to get real close to a foreground subject and still have a vast depth of field. This also greatly exaggerates the relative size of foreground and background objects giving a sense of z-axis movement, a feeling that we could walk into the image. Here, the foreground rocks are about half a meter tall and the waterfall in the background is over 50m high.
Aiku Otaki Waterfall, Miyagi - Japan

Canon Kiss Digital X with a Canon EF-S 10-22mm f/3.5-4.5 USM at 22mm EFL and 3 stop ND filter on a tripod. Exposure Trio: 2.5s, f/11 & ISO 100.
Another advantage for a wide angle lens is the relatively slow hand-holdable shutter speed. With an EFL of 16mm, the general rule is 1/16s. With a little extra ISO, this often makes a tripod redundant, even after the sun goes down. I quite like it for doing hand-held street photography. Especially after it rains, when the streets are much more reflective and colourful.
Wet Streets, Kagoshima - Japan

Canon Kiss Digital X with a Canon EF-S 10-22mm f/3.5-4.5 USM at 16mm EFL. Exposure Trio: 1/15s, f/3.5 & ISO 800.
Now most zoom lenses are not without their faults. It's got some barrel distortion at the wide end and some pin cushion at the long end. However there's a sweet spot somewhere in the middle where there's almost no distortion. For this lens that's at 17mm or 28mm EFL. A nice focal length for architecture. And if you have the space to step back and don't mind cropping, you can get the effect of a tilt-shift lens for free. Just keep the camera level (not up or down) and all your architectural lines will turn out straight like they're supposed to be.
St John's Church from Kyoto at Meiji-Mura (Architectural Museum), Inuyama - Japan.

Canon Kiss Digital X with a Canon EF-S 10-22mm f/3.5-4.5 USM at 28mm EFL. Exposure Trio: 1/80s, f/6.3 & ISO 100.
Zoom all the way in for 35mm EFL and get a nice focal length for environmental portraits. In this case my subject was an old cart, slowly being reclaimed by the surrounding vegetation.
Old Cart, Chiran - Japan

Canon Kiss Digital X with a Canon EF-S 10-22mm f/3.5-4.5 USM at 35mm EFL. Exposure Trio: 1/200s, f/4.5 & ISO 200.
That's certainly not all this lens is capable of. There are as many uses for this lens as there are owners of this lens. These are just a few ways that I put this lens to good use.