I'm really digging Person of Interest (LOVE Jim Caviezel!!!!!!! and so good to see Michael Emerson on the screen again!!!)
Also, I started watching The Secret Circle, and other than CW's total teenage-aimed audience, it's pretty good too. And I really am liking Ringer. Good unfolding mystery there, and of course I'm a Buffy fan, so it's fun to see SMG on screen again, as well. I really haven't tried any other new shows.
As for returning shows, I love Vampire Diaries, Bones, Criminal Minds, Fringe, and I'm all about True Blood, Dexter, Spartacus, and other HBO/Showtime/Starz shows.
But I really try to not watch too much TV. My butt doesn't appreciate it that much.