I don't think that "all" africans can be kept together but many of them can. Some are not quite as agressive as others. I believe that most with "zebra" in the name tends to be more agressive than say a yellow lab. Other than that I have no idea. I'm sure someone will come along with more information as I'm still rather new to cichlids!
Your best bet is to come up with a list of ones that you like, give the size of your tank and what not, and someone can help you a little better.
Actually scratch that... post in the cichlid section if you haven't already or have a moderator move your post for you.