The Africa expat wives club forum is going quite well I think. Forgive the rather basic format, but I am not very handy with computers so haven't done much to the template. The forum is full of queries from people moving to Nairobi imminently or questions from those who have arrived recently. If you are in this position, please do log in, post comments there, chat to me (i.e. to get Africa expat wife recommends or local tips) and hopefully chat to others who are in a similar situation - it might help with the transition to do a little social networking on the forum before you arrive.
I always found that my best expat friends arrived in town at roughly the same time as me - this is because you generally have a lot in common being on the same point of the learning curve at the same time.