There's a new service coming soon, that'll let you find out when your favourite program/film/actor is next appearing on the TV in your area. It's called LocateTV. It's in (closed) beta right now, so all you can do is register, but I hope it's going to be huge. That's all I can say for now, but you can read the official story at the LocateTV blog.
This 'embed' image should change with time, always showing when the next episode of Dr. Who is on in your region.