Today on TV

Rules of Engagement (7 and 8:30 p.m., Ch. 2): It's the last two episodes of the season — and, if we're lucky, the last two episodes, period — of this bad sitcom.

Dancing With the Stars (7 p.m., Ch. 4): The finalists perform.

Gossip Girl (7 p.m., Ch. 13): Gossip Girl sends out a shocking e-mail blast during the commencement ceremony.

How I Met Your Mother (7:30 p.m., Ch. 2): There's a big development in the Barney-loves-Robin plotline. And if you're holding your breath to find out who the mother is going to be, start breathing again. Immediately. (Season finale)

Two and a Half Men (8 p.m., Ch. 2): Charlie's ex-fiancee is back in town. (Season finale)

The Bachelorette (8 p.m., Ch. 4): Jillian Harris, who was chosen and then rejected on "The Bachelor," is back looking for love. Because some people never learn.

American Experience (8 p.m., Ch. 7): A history of "The Kennedys."

24 (7 p.m., Ch. 13): The last two hours of this terrorism-filled day play out as the season comes to an end.

One Tree Hill (8 p.m., Ch. 30): The soap froths to ridiculous heights in the season finale.

CSI: Miami (9 p.m., Ch. 2): Horatio tries to save Yelina. (Season finale)

Medium (9 p.m., Ch. 5): Allison dreams about a kidnap victim (Rumer Willis) rescued by Cynthia (Anjelica Huston). (Season finale)

Greek (9 p.m., ABC Family): Dale and Rusty try to infiltrate a secret society on campus.