How long does it take to fly from Earth to Mars?

This depends on the distance between Mars and Earth, which changes as the two planets' orbits take them further apart and closer together. During the Mars minimum, the day at which Mars and Earth are closest together, Mars is 55,746,199 km from Earth. If a spacecraft were to travel at the speed of sound (761 miles per hour or 1217.6 kilometers per hour) then it would take 45783 hours and 36 minutes. In other words, it would take 5 years, 82 days, and 15 hours if travelling at the speed of sound.

the above take from:
http://wiki.answers.com/Q/How_long_does_it_take_you_to_get_to_Mars_from_Earth

Although much greater speeds are easily attained in space.
The latest mission by NASA, saw the Phoenix Lander get there in 294 days.

https://en.wikipedia.org/wiki/Phoenix_(spacecraft)

A neighbor of mine back in Israel was, in the 1960s, on a crew selected for possible missions as the first to go to Mars. He still remembers the basics of what would have been his mission - it would have taken him about six months from the launch to arrival in Martian orbit.