Speaking activities that compel students to be creative and think on their feet are a good way to expand vocabulary and increase confidence. Try an improv contest; after explaining the concept of improv, split students into teams and give each team a different situation. For example, three friends waiting in line to see a movie when they hear that it is sold out. Or let students, in teams, choose a well-known movie and re-enact a scene from it. Other teams try to guess the movie. For a unit in current events, let students pick a controversial situation and re-enact how they believe it went; for example, the Middle East peace talks. This sparks debate as well as creative use of the language.
A ticking clock can help students learn to think on their feet. Send students out of the classroom in pairs, then pick a category such as food, jobs or furniture. Tell the class which category you picked. Call in the first student and give her 30 seconds to name as many objects in the category as she can. Then call in the next student. He must do the same thing, but cannot repeat any of what the previous student said. Or split the class in half and tell them they have one minute to line up in descending order according to their birthdays. They must speak only in English.
Friendly competition in the EFL classroom is frequently engaging and fun for students. Play "Hot Seat" with your students: split the class into two teams, then choose one team member from each team to come to the front of the room and sit with his back to the board. Write a vocabulary word on the board. Teams must describe the word (without saying it) to the team member at the front, who must try to guess they word they are describing. The first team member to guess the word wins a point for his team.
Or try a "Family Feud"-style game with students to test their knowledge of grammar points. Use two teams. One student from each team comes to the front on either side of a table. Read the clue; for example, "A sentence in past progressive," "A sentence with two subjects" or "A sentence in future passive." The first student to slap the table gets a chance to answer correctly. If she does, her team gets a point.
Debate activities give students the chance to express their opinions and work on their reasoning skills. Split students into teams -- one team for every side of the issue. Choose a polarizing issue in order to generate strong opinions. Politics is frequently a good source of ideas; for example, "Palestine should (not) be a sovereign state" or "Turkey should (not) be admitted to the European Union." So are activities that are closer to home, such as "Every person should be guaranteed a job" or "Religion in schools should (never/always) be banned." Give students a few minutes to organize their thoughts, then start the debate. Keep it going with questions and try to poke holes in the arguments to get students thinking. Ask students directly for their opinion so that every student speaks.