I like doing this activity at the end of a unit, I ask all the students to write a tweet (140 characters max!) about what they learnt, what they found difficult or a question they have concerning the work they have done. Sometimes we tweet it or sometimes the students write on these fun stickers I bought:
This way they can read each other’s tweets too.
Another end of unit activity I like is for each student to write a question on the board, and then they each go back up and answer someone else’s question. I find students teaching each other a very powerful tool, or maybe I’m just getting lazy!