I personally own and highly recommend the Panasonic Lumix FZ28 for taking on a safari holiday. The FZ28 is the newer version of the FZ18, but older than the Panasonic FZ38 camera.
It has all the features you are looking for in a good safari camera and because the latest version is now the FZ38, you can pick up the FZ28 at a really good price.
Now I know there are many of you that may say surely a digital SLR camera is better and you are mostly right, but they do have their down sides - read more on why I recommend a superzoom over a SLR camera here > SLR vs Compact cameras for Safaris.
Before choosing my camera, I did alot of research and eventually decided on the Panasonic FZ28. It has an awsome super-zoom with it's 18x optically stabilised lens (27-486mm, 35mm equivalent).
On top of this and is what I have done is to add a 1.7x teleconverter to it, which you can either get from Panasonic, or there is a cheaper version produced by Olympus, the TCON-17 1.7x Tele Conversion Lens. I highly recommend this as you can get far closer to the action.