So lonely without new episodes of 24

24 was the first show I've ever actually watched on tv as it was progressing.
Usually I just watch reruns of sitcoms or shows like Stargate on dvd.
I didn't start watching Stargate Atlantis until the last episode of season 4, and season 5 was so stupid I couldn't stand watching it!

But now that I've started watching something that is new every week, I like it!
So I need your help, I'm going to be watching Castle online since it ended already, but after that, what active tv show should I pick up on?