Dictionary.com defines a commonplace book as "a book in which records are made of things to be remembered". This is my commonplace book.

History

Writings and statements by others about history.

Security

Writings and statements by others about security.

Fiction

Favorite passages from works of fiction.

52 McGs

Notes from 52 McGs: New York Times obituaries.

Various

Notes, thoughts, and writings about virtually any subject, as long as it's interesting.
WebSanity Top Secret