The Outlander Series, by Diana Gabaldon. The 8th book in the series comes out later this year, and there's also a movie being released this summer (
Ron Moore is doing the adaptation/producing, Starz is carrying it).
The books in order are:
Outlander
Dragonfly in Amber
Voyager
Drums of Autumn
The Fiery Cross
A Breath of Snow & Ashes
An Echo in the Bone (just waiting for the jokes with that one, lol)
The 8th book that will be released in June is Written In My Own Heart's Blood. There is a spin off book series from Outlander, known as the Lord John books/series.