How would you make a game instances list?

I've seen this in Apocalypse Rising, and thought it was only that games very good scripting that has done it. However, I've began to see it in some low end games that don't have as much scripting, and now have wondered how to do it. How do you list all of the server instances in a scrollingbox and then join them? I've been wondering this for a very long time and would like to see if anyone here is able to explain it to me.