Overlanding and General Advise...

Safety - no better or worse than anywhere else, just be sensible.
Overlanding - how most of the population get around, you should be able to find some kind of transport going your way.
Flights - flights between different countries are expensive, generally internal flights are less so.
General - it's a fun continent, you can't help but enjoy yourself!
Vaccines - you'll need yellow fever & malaria pills, minimum. See your doctor.
Travel tip - always have some loo paper in your pocket

You may be new to travelblog, but you have posted similar questions here on Thorntree in the past.

Before going any further, it would be helpful to know your total budget for all this. Africa is more expensive than you might think, especially with all the internal flights you would need. You may need to scale back your plans.

Peace,

BB

This is not travelblog.org, and you've posted this same message on Lonely Planet several times. It looks like you're posting a huge list of questions everywhere so you won't have to do your own research. If you've done "extensive reading," you should already know the answers to most of your long list of extremely general questions, some of which, such as vaccines and visas, are answerable in a simple Google search. If you've done extensive reading, your questions should be a lot narrower in scope.

You don't tell us anything about your preferences as far as what you're interested in seeing. How can you expect any relevant answers?

If you had a few specific questions, maybe you'd get the answers you're looking for.

Yawn!

Ah, bigbri and safuwa, good work!
The OP apparently was planning a 6 months trip in october 2008 , december 2008, in june 2009 again in june 09 then october and november 2009... Dude, you've been (supposely) planning this trip for over a year, and still come back with such broad questions... almost never answer to anybody except to ask even more broad questions (any tips about visa/meds/great places to see/what to eat for dinner/ what should I do with my life?) James, what's your point? wasting people time?

Your anger is misdirected. I highly suggest this book:

The Anatomy of Peace

Hi jamesbruce,

As others have noted, such broad questions are very difficult to answer on a forum like this. Try some more specific questions you have about your trip, and next time don't insult the other users - really not the best tactic if you're looking for others to help you. Once you have a plan for your trip, come back with some specific questions about details, lesser-known places & side trips, etc. and you'll get better results.