Here are some books and other resources I use for my library lesson plans. I create a lot of my own material, as well. If you're looking for my library lesson plan resources, look on the right side of my website under Library Lesson Plan Resources!
There's a Complete Library Skills book for every grade level K-6. Some of the information is outdated (there is still a section on the old school card catalog, which I haven't used in probably 20 years), but there's also some really great activities in these books. One of the books I keep going back to again and again.
The 21st Century Elementary Library Media Program is not a lesson plan book, but it does offer some good ideas for library media specialists who want to make the most of the resources available to them. There are lots of good ideas in this book.
New on the Job: A School Library Media Specialist's Guide to Success is for new Library Media Specialists. It covers many topics from vendors to collaboration to challenges of the job.