The Pride and Prejudice BBC series from the 90's is pretty universally regarded as a near-perfect adaptation of the book.
Neil Gaiman is also apparently very happy with how faithful the Good Omens show was to the book (and he worked on the show, which is probably the reason why).
Speaking of Neil Gaiman, the Stardust movie is one of those examples of a movie that, while not quite faithful to the books, is still a great adaptation and a great movie in its own right.
The Princess Bride is another great example of a book that was adapted well. Gone with the Wind too.
And of course, Lord of the Rings. Even though the movies diverged heavily (and I mean heavily) from the books, they were so well done and faithful to Tolkien's overall vision that I think they rightly deserve the place as one of, if not the, top book to movie adaptation of all time.