An interesting story on the NASA Science site a few weeks back pointed out that magnetic north is on the move.

Earth's Inconstant Magnetic Field

"The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating "to 40 km per year," says Newitt. At this rate it will exit North America and reach Siberia in a few decades."

There's a lot of interesting info in the full article, including what happens when the entire field flips,

"They come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago. Are we overdue for another? No one knows."