The Outlander series by Diana Gabaldon is really good, if you don't mind a little romance.
Doomsday Book/The Oxford Time Travel series by Connie Willis.
Century Rain by Alastair Reynolds: not time travel exactly, but it's basically people from the future (around 2270 or so, I think) visiting a version of 1959.
11/22/63 by Stephen King. I haven't read this one yet, but it's gotten decent reviews, so it's probably good.
Farnham's Freehold by Robert A. Heinlein- this is one that goes to the distant future rather than the past. It's a bit dated and very politically incorrect by modern standards, but it's a pretty interesting book. Heinlein has several other time travel stories also, but I haven't read them.

To Say Nothing of the Dog - by Connie Willis - this one won a Hugo, and is one of my favorite books.
End of Eternity - by Isaac Asimov - a classic.

The "Outlander" series by Diana Gabaldon centers around time travel and is pretty epic (7 books and counting?). They're some of my favorite books ever, but I admit that any description you'll find online (or on the back of the book, even) will make them sound terrible. They're good, I swear!

I read this book called Timeline by Michael Crichton many years ago and I recall it being pretty good. The movie based off of it sucked, though...

Infinity Ring is good. Two books to the series so far.

Well, there's Ward Moore's classic Bring the Jubilee, and Anthony Boucher's novella -- you'll have to find a collection of his works -- Barrier, which put a great deal of thought into the subject and built a compelling story around it...

Stravaganza series by Mary Hoffman...sort of... alternate universe time traveling rather.

'The Misery' by Stephen King.