This is a simple way to finish off a lesson. Arrange lots of keywords around a circle on the board, and ask students to try to create sentences that link those keywords together.
If you have an interactive whiteboard you can get students to come up and drag the keywords they have used in their sentence into the circle. You can then take the words back out of the circle to let other students re-use them, or you can leave them in the middle so that students are forced to use the remaining (probably more difficult) words on the outside.