commonplace book n. a book into which noteable extracts from other works are copied for personal use.
A commonplace book is basically a personal collection of diverse bits of information. Often a collection of quotes from classical authours commonplace books of the early seventeenth century contained household accounts, music, poetry, copies of correspondance. Pretty much whatever was useful to the owner who was also usually the creator.
My commonplace book (this online version anyway) is primarily focused on period texts and illustrations that provide information useful for my living history persona. Some of the items are more useful than others but I choose to share them all because someone might want to use the information someday.
I have organized this commonplace book by broad themes. Subject headings were included in a sixteenth century pre-printed commonplace book. This book had an introduction and and index that pointed to subject headings on numbered pages which were otherwise blank. The owner was supposed to fill in the texts under the appropriate heading thus allowing for easy reference. My subject headings are neither as comprehensive nor even thematically similar to period works but the web is not period appropriate anyway.
I have long thought of using a real blank book as a commonplace book. It would be both a place to practice my atrocious calligraphy and a period activity and reference all in one. For right now however I have better things to do with my time (like make this online version bigger and better.) I actually did use a small artists sketchbook for a time which contains my notes from a Pas d'Armes and the petition for SCA branch status for S. Giles College. The writing was in modern printing not even modern cursive which is closer to some period hands than you might imagine.