I found these cool clips at Lakeshore Learning. (This is not a paid advertisement. I just like to share about products I think are great.)
We've used these a couple different ways. On the following occasion, each kid chose a different book about a Renaissance artist. They were also given one of each different clip. As they read their books, they inserted each of their clips so they would be able to remember the important things they learned. When everyone was done, they took turns teaching each other about the artist.
This time, I had 4 books that I wanted everyone to have a chance to look at. They had 10 minutes to skim the words and look at the pictures in one book, and then we rotated books and set the the timer again. They were required to find at least 1 interesting thing and put an arrow on it. When everyone was done with every book, we went through and they each were able to say why they picked that page to be highlighted.
I found that these arrow clips kept the kids focused on what they were reading or seeing on the pages. It also helps them retain the info they're learning if they have a purpose ("Where can I put these 'cause and effect' markers?") and an opportunity to teach each other. They also would be helpful for when the kids do non fiction reports, instead of taking notes on paper as they read. They can use these and then go back and look at them later to write their reports.