Divination
Some psychics and practitioners of magic use the reflective surface of a mirror by the light of a candle to induce visions. It is believed by these people that the mirror acts in the same way as a crystal ball-- a reflective surface is the ideal place for the mind to project the visions that come.
Bad Luck
To this day, who doesn't shudder when accidentally breaking a mirror? It's been drilled into our consciousness that seven years of bad luck will ensue. I don't know about seven full years, but this idea dates back to the idea that the mirror traps souls. When your break it, it frees the angry, trapped souls from within who then have nowhere to go and nothing to do but haunt the nearest person-- the person who broke the mirror.
Good Luck
Feng Shui, the Asian art of arranging a home for optimal flow of positive energy, has a lot to say about mirrors. Using mirrors to visually expand a room and bounce more light into it also expands fills it with beneficial energies. If there are any areas in the home where the energy gets trapped or doesn't flow properly, a carefully placed mirror can help redirect the energy to a more productive flow.
In feng shui, mirrors are believed to bring calm. They have the same effect as the element of water, probably because their reflective surfaces are reminiscant of a still pond. Round mirrors are brought in to attract abundance and wealth to the home.
So, should we just write off mirrors as fantasy fodder? Perhaps… or perhaps we should give a little more thought to the mirrors we bring into our homes, where we place them and how we treat them. Maybe there is more to them than what they seem to be on the surface.