Go over the mistakes of the previous week. If there was a project on writing about a hobby have the students read what they have done out loud. This could be combined with a presentation where the student is asked to go to the front of the class and show off their hobby.
Talk about what they think about their respective hobby. Give the student specific parameters and see what they would do with their hobby. So if the student has a penchant for collecting stamps ask him what he would do if he were collecting mint stamps or first day covers. These terms could be written on the board and explained briefly or tossed out to other students.
A demonstration of a particular hobby can be done by taking out model cars and having the student compare the different models so that sizes, colours and models can be discussed and compared. Students would then be encouraged to draw a chart where they would list these characteristics and then discuss them.
Grammar can be included by integrating exercises such as if I were a model car collector I would…and then have the student continue the sentence on his own. Scrabble can be included as an activity if you need the students to increase their vocabulary or just as something to complement other word building techniques.
Having a film on how hobbies are done would be ideal to integrate listening skills but anything regarding dialogue and good visuals will help. Even having a tape recorder available would work well although these days a videotape or DVD is much more popular in the private schools.