I love time travel books.  Where someone from one time period finds themselves in another time period and gets to explore and adapt to it.  My favorite is Time and Again by Jack Finney.  What are your favorites?

One of my favorites is Susan Macias's COURTNEY'S COWBOY. A modern day couple, experiencing troubles in their marriage, find themselves back in the old West. Keeper shelf.

Also, Shelly Thacker's FOREVER HIS. Contemporary woman is swept back to Medieval times, and goes through the usual period of adapting to the era, but the author's take on how the Medieval people look on the things she brought with her is cool. Keeper shelf. The book ties-in with another Thacker, HIS FORBIDDEN TOUCH.

Have read other time-travels but these two have made the most impression on me.

Gail

Without a doubt - Oultander series - Diana Gabaldon.  Also like Karen Marie Moning's Highlanders series. 

Sandra Hill's viking series is laugh out loud funny. I love how the vikings misunderstand modern language. 

Barbara Bretton did a series years ago, Somewhere In Time, Tomorrow & Always, and Destiny's Child.  I love all 3 of them.

I second MK on Outlander.  Also The Troll Bridge  by Patti O'Shea.

Years ago, Jasmine Cresswell wrote two good time-travel/historicals:   TIMELESS and TO CATCH THE WIND.   The first brings a heroine back to 1745; the second brings a heroine to the reign of Charles II of England (as Charles' queen).    I don't usually like time travel so I consider it fortunate I was able to find these & really enjoyed them.

These are my favorites:

Outlander by Diana Gabaldon 

Once a Pirate by Susan Grant

A Love Through Time by Terri Brisbin

Journey to Yesterday by June Lund Shiplett

The Winter Sea by Susanna Kearsley

A Knight in Shining Armor by Jude Deveraux

I second A Knight In Shining Armor . One of the few romances/time travel that I have read twice.

I'm copying my post on the subject for your message on the historical fiction board, since I am too lazy to type it again.

Outlander is of course the best time travel series out there, but I would also recommend the Alex Balfour series by Allen Appel.  There are four books in the series  - Time After Time, Til the End of Time, Twice Upon a Time, and In Time of War.  The way the fourth book ended just screamed, sequel, but so far, it hasn't appeared.

The time periods traveled to in this series include the Russian Revolution, Little Big Horn, World War II, and the Civil War.

I like the Janet Chapman books with the Highlanders brought forward several centuries.

I'll have to look for those Barbara Bretton books.  I lover her Sugar Maple series.