Are there any regulations for shipping magnets?

According to the United States Department of Transportation and the Office of Hazardous Materials Safety, the limit forshipping magnets by air is a magnetic field strength of 0.00525 Gauss measuredat 15 feet (4.5 meters) from any point on the outside of the package. 

There are no restrictions on the shipping of magnetized materials by ground. When in doubt, ship magnets by ground transportation.