Head over and get your free Popular Science magazine subscription!! This went super fast last time, so good luck. I just signed up and there is no catch! No credit card needed, no bills will be sent etc.
My response when I finished the form was:
As usual, it takes 6 to 10 weeks for your first issue to arrive. After your first issue arrives, you will receive uninterrupted service and you will not receive any bills. Sorry, no substitutions.