Thanks for all the great ideas! I'm now thinking about bowl cozies with a jar of homemade soup mix inside. Found a great recipe for various types of soups-in-a-jar somewhere online. I can tie each cozy and jar up with a nice bow and some instructions, of course.
As for bookmarks, as a librarian, I don't really like fabric bookmarks because they are often too thick and stress the bindings. I do like paper ones, or the fabric triangles you can put over the corners, though.