Mine is a carboard with second hand paper (think used calendar pages, old printed pages) and a strong clip added over the top. Whit this kind of paper I use the other side of the page. I do this to sort of give it a second life. Also this is for notes during the session, this is then rewritten for Campaign Logger once I have time.

I do this both as a GM or as a Player because I like having good notes. In some games, when the game finished, I contact the GM and give him a list of the added NPCs he used, because sometimes my notes are more detailed than his.