This is one of my favourite ideas. It taps into libraries as places with facts and information: facts and information can can be fun and light as well as heavy. It offers the opportunity for some fun interaction when you hand over the book and bookmark. It recycles something you can find in op shops on a reasonably regular basis.
It's probably a slightly pricier idea than some of the other ones from this week, but here's a comparison. A commercial library supplier I checked had quite a few bookmarks which came in bundles of 200 bookmarks for $40. In this box of Trivial Pursuit I got 200 bookmarks for $4. A tenth of the price. Still cheap as chips, and fun! (This idea is part of my presentation about Re-Imagining your School Library: I've presented it in Newcastle and south-western Sydney in the last month, so I know there are TLs in those areas scouring their op shops and garage sales for Trivial Pursuit!)
Links in again with a theme of the library being a place where you find facts and information (and fun, the unexpected, a happy moment) - oh, there are lots of ways you could tie this in to a wider promotional theme.
Hope you've enjoyed the Cheap Bookmark Week ideas on the blog this week - do comment, your feedback is always appreciated.
*GIFSL = good ideas for school libraries, an ongoing series on this blog.