Check out
Catalyst: A Conversation Taskbook for English Language Learners. It's completely self-contained with lesson plans, targets, review, assessment and a topic creation mechanism built in.
Topics are relevant because they are created by the students themselves. Students are trained to respond spontaneously and will be conversing in a matter of seconds, sidestepping that messy little dance that instructors and students of such classes typically engage in while attempting to negotiate a topic for the day.
Instructors will actually have very little prep to do beyond understanding the lesson
du jour.
You can find out more here:
Catalyst: A Conversation Taskbook for English Language Learners