Many photographers of all skill and interest levels purchase a SLR camera with a zooming kit lens. After a while they purchase 1 or more other zoom lenses. Very few people consider getting a fixed focal length lens. These lenses have no zoom, and the lens elements stay a constant distance from the image sensor.
What does this mean to you?
A fixed lens is incredibly fast due to a very wide maximum aperture. This allows for easier night shots and cool depth of field tricks. Instead of zooming with your camera, you "zoom with your Nikes." I personally find this to be a neat limitation that boosts my creativity. If I see something that I want to take a picture of, I can't just zoom in or out to make it fit when I'm sporting a fixie. Instead I have to walk around to find a rewarding angle and distance from the subject. Currently I have a fixed 50mm lens that's my workhorse. I also have a 28mm that gets a lot of use as well. Most days these are the only lenses that I carry, and my zoomers just collect dust on my desk.
I would highly encourage anyone who has never tried a fixed lens to go get a 50mm. Fantastic ones can be found for about $100. Leave me an email or comment if you have any questions about them.