Marianne Curley's The Guardians of Time trilogy (starting with The Named) is about young people who travel through time to save the world as part of a job-thing.

She has another book involving time travel, Old Magic, but it's not so controlled travel.

To Say Nothing of the Dog by Connie Willis is the only book I've read in the time-traveling historian universe.

The Prisoner of Azkaban! Possibly my fave of the HP movies.

Another vote here for TO SAY NOTHING OF THE DOG by Connie Willis. One of my all-time favorites! I haven't read BLACK OUT/ALL CLEAR yet, and I liked (but did not love) DOOMSDAY BOOK. I did like the way she has time travel work in terms of "rules".

Other than that, Dr Who is most definitely my favorite time travel story...

I think that new book RUBY RED is about time travel? Have not read it though.

I just remembered that one of my favorite bloggers does a time-travel feature every Tuesday: http://charlotteslibrary.blogspot.com/p/time-travel-books.html

Perhaps there's something there that might be of interest?

Children’s Books:

THE CHRONAL ENGINE, by Greg Leitich Smith (Clarion 2012).

THE SWITCHING WELL and 11,000 YEARS LOST, both by Peni Griffin, but I believe their time travel is an accident.

Hemphill/Riddleberger STONEWALL HINKLEMAN AND THE BATTLE OF BULL RUN uses some magical devices.

On screen:

The Star Trek episode CITY ON THE EDGE OF FOREVER is probably one of the better uses of time travel on the show (there were also a lot that weren’t so good ).

KATE & LEOPOLD, with Hugh Jackman and Meg Ryan, is charming.

BILL & TED’s EXCELLENT ADVENTURE has some nice time travel elements.

BACK TO THE FUTURE (at least the first one).

HEROES tv series. Some of the time travel is inconsistent, though.

General:

Nahin’s TIME MACHINES: TIME TRAVEL IN PHYSICS, METAPHYSICS, and SCIENCE FICTION has a pretty good rundown of time travel stuff both theory and discussions of movies, books.