That is a very good idea from Lucy.
Also you can use speaking activities in class where all students participate, and it is not optional. For example with a discussion or a debate it is very easy for a few students to take over and for others to remain on the side lines.
So speaking tasks where joining in is part of the structure of the activity are better in many ways. A couple of obvious examples are presentations or role-plays. Here's a simple fun variant on the idea of giving a presentation in class.
Students have the challenge of talking for one minute on a topic. This can be done as a serious activity where the student is allowed to prepare in advance. Or it may be done as a light and fun task. One does not always need to discuss earth-shattering events or big social problems. Sometimes it is nice to lighten up and discuss something like "my dog", "my sister" or "pencils".
Discussing pencils for a minute is by no means necessarily easy and can require a vast vocabulary. One can talk about the size, shapes and colour of pencils, what we use them for and the marvellous fact that we can erase what we have written. Alternatively a student might talk about how one morning her pencil refused to come to class with her. She tried to bribe it into coming by promising a biscuit at break time but the pencil refused to budge, saying it needed more sleep and was sick of working the whole time anyway. And so on with any old rubbish for a minute.
The purpose of the task is to get the students talking and enjoying themselves. To start out with this could be done in pairs to spread the talking time between the two. Students could have a minute to prepare and then stand up and deliver, either solo or in pairs with one student asking questions and the other replying.
At the end of the minute the speaker gets to ask the class a question about the content. This gives the students who are listening a reason to listen, instead of just sitting there passively. Alternatively while the talking is going on the teacher can prepare questions and give the whole class a quizz from the talking sessions at the end. It's always important to give speakers a reason to talk and listeners a reason to listen.
There are lots of ideas for speaking, either for accuracy or fluency in my book and you are welcome to try out the free samples that come out by email.http://www.teachingenglishgames.com/adults.htm