I got this idea from the Choice Literacy website. It was in a video done by The Sisters. They were showing parts of their classroom and they showed a space on their wall where they kept track of the books that they had read aloud to students. When they finished reading a book, they simply wrote the title down.
I have found this simple little thing to be very powerful for my students. They never forget to remind me to write down the name of a book we have read. We label books as being poetry, non fiction or fiction. This helps us to see where we need to expand as readers. I also think that having this list in a place of prominence in our classroom helps them to feel proud of the amount of reading that we have done.
I made the log out of the paper used to cover bulletin boards. When the list got too long for the board, I simply rolled the top of the paper around a pencil to create a scroll.