I teach a lovely year 10 group this year. Intelligent and polite and a generally nice bunch of kids to chat to and teach. Every week, they're invited to join me after school for 'Warty Wednesday' - a revision session so-called because this is the day that one boy in the class has his warts removed. Typically, about 10 kids turn up and we do some relaxed revision on topics we've already covered.
This week was 'Area and Perimeter' - up to and including parts of circles and compound shapes involving them. I don't like to prepare too much for it, so I made an A3 sheet with shapes on it and arrows where I wanted them to write dimensions. When they came in, I asked them to write a dimension on every arrow - this would be their sheet. We then passed this clockwise to the next person who found the area and perimeter of the shape with 'my' dimensions. After a short while, we passed them on and I asked the next person to receive the worksheet to check the work of the previous person before moving on.
At the end of the session every pupil should have had a sheet with a variety of area and perimeter questions and other people's work for them to look over and revise from.
I'm sure there's a lot of mileage in this - either with small groups, or in class having tables pass them around (if the seating plan suits) or along rows (if your seats are like this) - and can be extended to basic probability (colouring in dots instead of writing measurements), calculating averages (writing a given amount of numbers for those around them to calculate) or even setting each other different questions for basic number work.