Make it real: successful ideas for role-plays

We launched Tuesday Speaking classes in our school and this has set me thinking.... how to get students to talk so that they feel relaxed and motivated?
There're lots of speaking activities, but to be honest role-plays are my favourite.
Role-plays, or simulations are one of the ways we can ease students' transition into using
English in real world situations. A simulation is where students act out a real-life situation, for example checking into at a hotel, but do not act out a different personality. Role-plays are where students take on different personalities. In a role-play, for example, one student may be asked to take on the role of "an angry neighbor" which is out of character for the student.
Role-plays are interesting, memorable and engaging. In their assumed role, students drop their shyness and start thinking in English.
What is important for a successful role-play? Preparation and a "hot" topic. The thing is it's not that easy to find a good role-play. And I'm always happy when the course book offers something really good, e.g yesterday we had a nice time with Business Result role-play (Unit 6 Solving crosscultural problems)

Role-plays can range from 30 minutes or one hour to a year-long corporate simulation for business English. Staging role-plays can be challenging for a teacher, but is also great fun. After you have done a few, you will know what to expect and feel more confident.

My experience is students love them and often leave the classroom laughing and still discussing the topic!

BTW I found a really great resource on role-plays. It's a presentation with ready-made roles:)

http://dl.dropbox.com/u/4392166/Methodology/Role%20plays.pdf