Rebecca,
There are many parts of H.323 and Sip that you could possibly break your report down to. There are endpoints and gateways, gatekeepers, session border controllers, SIP servers, etc. I think you focused on the top level subjects, but drilling down to the pieces of the main points is where you will be able to get 3 and more topics from. If it must be at a high level, then you can report on Megaco as well. Good luck.
Mike