Booksaver, the other thing you can do with Christmas cards is make gift tags. They won't have the to: from: words on but I cut out a piece of something with a pretty image on it that leaves room to put my names on. I have so many pretty ones in a box to use every year. I try to match them in color or theme to the wrapping paper, or just something the recipient would have a liking for.
I do have a couple bookmarks I've made from the cards too. I need to make some more of them. I always use my bookmarks because I NEVER dogear the corner of a page to mark. Hate when I take out a book that has corners dogeared. IMO that damages the book. I always try to straighten those corners out, but it always leaves a mark or damage.
Never thought of leaving bookmarks at the library for people to take. I wonder if they'd allow that? I have brought books home, though, that had bookmarks inside. Always thought somebody just forgot to take theirs out.