Megabus is giving away 200,000 free tickets for travel between January 9th and February 28th (US and Canada only). Winter is a slow travel season so I find plenty of free seats available:
There is a 50¢ booking fee per transaction so it's better to book multiple tickets at the same time.
Even though Megabus may not be a glamorous way to travel, I'll take it in a heartbeat for $0 50¢, especially for travel within the tri-state area.
(Hat tip to Pearls of Travel Wisdom)