http://www.greyhound.com/deals/military_discounts.shtml

Greyhound is proud to carry those who serve our country. Active duty and retired military personnel and their dependent family members may receive a 10-percent discount off the Greyhound walk-up (unrestricted) fare. Another option for military personnel is to travel on Greyhound for a maximum fare of $198 round trip anywhere in the continental United States.