A good resource is <http://www.cichlid-forum.com/profiles/category.php?cat=2>. You can also go the original "profiles" page and look at other types of cichlids also (if/when you get other tanks and things).
The link I provided will take you to a list of most (if not all) the mbuna that are available in the hobby. I have only kept the red zebra (M. estherae) and can say that I have one that is just over 5" and another that is quickly approaching 5" and both seem to still be growing. You can look up their average adult size on the link I posted. Also, as you try to find other fish to stock the tank with make sure to look at aggression level. Try to keep their levels the same (highly aggressive with highly aggressive, and mildly aggressive with mildly aggressive). You can mix aggression levels somewhat, but when you mix the extremes you are taking a chance. I will add that specific fish have their own personalities so just because yellow labs are usually very peaceful sometimes you will get one that is highly aggressive.
Also, I won't say that it is necessary, but it can be helpful to keep species groups (4-5 of a specific species) with a ratio of 1 male per 3 females. This ratio does not apply to every species (such as demasoni, where you want a group of no less than 12 usually), but is a good rule of thumb.
Good luck!!!