Do you need to get your students involved? You want them to be truly engaged in their work?
My best suggestion to you is for YOU TO GET INVOLVED TOO!! There is nothing more exciting for the students than to see their subject teacher participating in the activity along with them.
Remember how great you felt when your PE teacher would run with you in your class? (My hat comes off to those teachers who can manage to participate with 8 classes!!!!)
Participation in the second language classroom is no different! When you are doing an oral activity with your students, get in there with them!! Be a full participant. Not only do you get to hear your students and are able to help them out along the way, but you are seen as not only a teacher who gets involved but your students will be able to see the "language" in action!
Market place activities are perfect for this and so are the inside/outside circle activities! Have fun and "parlez"! :)