In my intermediate level ESL class I have them do a discussion in groups once a week. The next day they write about the topic, and I put their responses on the Internet. (It's a CALL class, so they all read everyone's responses the next time they are in the computer lab. Of course, anyone can opt out by writing "private" on the paper.)
For the "themes" I took Education, Families, Food, Health & Exercise, Home, Jobs, Media, Money, Native City, San Francisco (That's where I am

) Environment, and Leisure Time. I grouped the opened-ended questions and explained to the class they are supposed to be "conversation starters." If they follow a tangent and don't get to all the questions, I don't care as long as they are engrossed and speaking English. If you want to see the results you can look at my webpage at
http://fog.ccsf.edu/~lfried/writing/studentwriting.html
You can see what the level of the students is from the writing. I correct grammatical errors, but I try not to correct too much, so it often sounds a little stilted. However, my students told me that was a highlight of the computer class. They enjoyed reading the stories and opinions of the other students.
I was going to put the questions on the web in case any other teacher wanted to adapt them, but I haven't gotten around to it yet. If you are interested, I'd be happy to email some to you if you send me a private message. In the meantime, here's an example on food:
1. What kind of food do you like? What kind of food do you dislike?
2. How are American eating customs different from those in your native country? How have your eating habits changed since you first arrived here?
3. Is there any kind of food you can get in your native country that you can't find in San Francisco? What is it? What new kinds of food have you tried since you arrived here? Which ones do you like? Which ones do you dislike?
4. How do people shop for food in your country? How often do they go shopping? Where do they buy their food? Directly from farmers? In supermarkets? In small stores? In indoor or outdoor markets?
5. How often do you eat in restaurants in San Francisco? What kind of food do you usually have? What's your favorite restaurant?
By the way, you need to be able to see Macromedia Flash for some of the titles, but it isn't important for the content. We have it installed at school, which is where I use it.