After the publication of The Lord of the Rings, Tolkien's publishers were looking forward to receiving the completed manuscript of The Silmarillion.  Unfortunately for them (and us!) Tolkien's attention was diverted from work on The Silmarillion by many matters, and publication was delayed until after his death. Tolkien certainly wasn't idle during this period, and the range of subjects that occupied him was no less diverse than in his earlier years.

In addition, the explosion of interest in Tolkien in the mid-1960s brought with it a flurry of magazine and newspaper articles based on interviews he gave and letters he sent.

1955-1962

The Adventures of Tom Bombadil

1963-1967 - Books and Periodicals

1963-1967 - Letters, Artwork and Miscellanea

Smith of Wootton Major

1968-1973 - Books and Periodicals

1968-1973 - Letters, Artwork and Miscellanea