I love to use mini sticky notes as bookmarks. They make a smaller version for just such a use, but rather than buy those, I make my own! Using leftover sticky notes, I cut them into strips perfect for helping me keep my place (or several places!) in my book. Works great for recipe books so I can find my favorites in a snap.
This is a great idea. I've learned the hard way to use bookmarks in novels to mark key points - like when major characters are introduced or clues are found. Then I can easily go back and re-read those parts, and I enjoy the book that much more. And your little sticky notes don't fly all over the place when I handle the book.