This activity is a great activity for a minimum day, or otherwise weird schedule, or at the end of a unit when you don't want to start new material quite yet.
I use this activity in my middle school math classes, but it can easily be adapted to other content areas (science, history, etc) and grade levels. This activity has students going through a text book, and previewing a section in a chapter. I went through and assigned each group a chapter, from which they flipped through and found a section to focus on. They had to preview it as a group and fill out the worksheet on what looks easy, hard, and familiar, and provide some key vocabulary and practice problems.
I made this a 2-day activity. During one period, students went through the chapter and filled out this worksheet. The next day, each group had to give a 3-5 minute presentation on their section and share their vocab words, explain what looked easy/hard/familiar, and walk the class through a practice problem.
The rubric I used for grading is provided below:
Group worksheet (5 points)
Group presentation (5 points)
**Everyone had to speak, or each person lost 1 point)
Taking notes on the other groups' presentations (10 points)
I emphasized that the idea isn't to become an expert on the section, but instead to be more like detectives for the class on what is coming up in the course.