I have used Quick Topic message boards for years. They are the simplest things to set up. They never shut down on you. They are like the energizer bunnies! I have used them for family conversations, for groups when we had to collaborate often, and to keep contact with a friend oversees. They have a free version and one with bells and whistles. I have always used the free.
Check it out sometime: http://www.quicktopic.com