Here’s an exhibit I plan on checking out in the near future: “The Diary: Three Centuries of Private Lives,” at the Morgan Library in New York.
The exhibit includes these lovely items:

A diary jointly kept by Nathaniel Hawthorne and his wife, Sophia Peabody Hawthorne:

John Ruskin’s chess diary:

You can see more images in the slides shows in these reviews:

New York Times: Tales of Lives Richly Lived, but True?
DNA Info: New Midtown Exhibit Peeks at Private Diaries of Writers, Performers.