According to The Futon Critic, TNT has acquired the off-network rights to Supernatural.
Repeats of the series will air weekdays at 10:00 AM ET, beginning on Monday, January 4. A special 10-hour marathon will air on Monday, February 15.
For the airdates, click here.
Source: The Futon Critic (thanks to SF Universe for the heads-up).
UPDATE: According to Cinema Blend, the weekdays timeslot is 10 PM, and not 10 AM, as reported by The Futon Critic.