Using students’ work in other classes can be stimulating and useful. Work done by one group of students can be shown to others at a similar level, or perhaps a lower one. I find that students creating the work for display are given a clear and motivating incentive; receiving students are in turn often intrigued and inspired by their fellow students.
When you receive some good examples of written work such as stories, descriptions, essays or letters, retain copies of interesting or stronger samples to use with other groups. You can display clean or corrected copies to the next group, but avoid giving examples covered in critical comments. Put up the samples on the classroom wall, or simply pass around examples. Invite students to respond to them, saying which they like and why. You could even use a strong sample as a model for a similar writing activity with the new group.
Audio recordings can also be a great medium. I recently recorded my intermediate students talking about what they had gained from their year in England, as well as any regrets or advice. I used an MP3 player and saved them as sound files. Students were told that their recordings would be played to new students the following term, thereby giving a clear target audience and purpose. Recently, my current students were clearly stimulated by hearing the other students’ impressions and advice.
Your context may allow you to do video tasks or even live demonstrations. Get students from one class to put together a mini show, demonstration or roleplay and to show it to the others. This might only take a few minutes, but it is likely to be memorable for the audience and also for the performers. It is also very much in line with task-based learning ideas: having a clear goal, an opportunity for rehearsal and culminating in a display.