I've got two, myself.
First there's
Adventures in Jimland which is a campaign system for exploration, which randomly generates terrain and natives on each blank map square as you enter it, and also has its own tabletop battle rules. With a bit of work it is adaptable to use as a campaign mechanism for whatever tabletop rules you want to use. Such things as dinosaurs are entirely optional, you can play it as a straight historical game if you want. One day I shall use it as the core for a 'Source of the Nile' campaign, but haven't got around to it yet.

Available from here:
http://minden_games.homestead.com/Jimland.htmlSecondly there is
Dark Continent, a role-playing game of African exploration. Of less use to a tabletop gamer perhaps, but chock full of interesting source material and written in quite a wry, humorous style. Worth having just as an enjoyable read. Not currently in print, but still crops up here and there. I was lucky enough to get a copy from Spirit Games a couple of years back.

I always wanted a copy of the board game
Source of the Nile , which had a hex map of Africa that is blank in the interior and you fill in as you go with coloured (wipeable) marker pens or crayons. Thought that might be useful for the campaign element of a miniatures game, but it is long out of print. Have yet to obtain this one, so can't really say if it is worth having or not.
http://boardgamegeek.com/boardgame/1577/source-of-the-nile