What's On Tonight: How I Met Your Mother, 24, Roommates, One Tree Hill

Sci-Fi has a Star Trek: TNG marathon all night.
TV Land has an Andy Griffith Show marathon all night.
At 8, ABC has a new, two-hour Dancing with the Stars, then a new Castle.
CBS has a new How I Met Your Mother at 8.
NBC has new episodes of Chuck, Heroes, and Medium.
The CW has a new Gossip Girl at 8, followed by a new One Tree Hill.
ABC Family has the season finale of The Secret Life of the American Teenager at 8, then the series premiere of Roommates.
TLC has two new episodes of Little People, Big World at 8.
Also at 8: BBC America has a new Top Gear.
At 9, FOX has a new 24.
USA has a new Monday Night RAW at 9.
At 9:30, Food Network has a new Will Work For Food, then a new Diners, Drive-Ins, and Dives.
At 10, TNT has a new Saving Grace.
A&E has a new Paranormal State at 10.
There's a new Ax Men on History Channel at 10.