If you are a teacher or someone who does public speaking, Aurora Talk is a great solution. You can write your presentation ahead of time in your word processor, then cut and paste it into Talk.

Talk will automatically format it to one sentence per line so that you can easily control the rate of your presentation. If someone asks a question, you can use F4 and F5 to answer yes/no questions, or if you need a longer response, you can switch to a different conversation, answer the question, then switch back in an instant, right where you left off.