There was a few errors in my earlier version, so this has been cleaned up. I'm sure I'll end up adding ones that I've missed later too.
Okay, I use the term "web 2.0", but chose a rather broad definition of that term. You'll see some mobile companies in there as well, since I believe the line is rather blurred in Africa.
If I missed something (which I'm sure I did), let me know in a comment or email and I'll add it to the 2nd iteration.