Duff Millipede:

This is a seasonal pest species of minor concern. It requires a moist environment, so modifying sources of high humidity such as plumbing leaks and basement cracks can often rid them in your home.

Photo: CSU Cooperative Extension Service

http://www.ext.colostate.edu/PUBS/insect/05552.html

http://www.ext.colostate.edu/PUBS/insect/05549.html