The YN-560-III is a great all around manually triggered flash that you can use to get started or if you are using Scott Hargis's Lighting Interiors manual flash technique. For details see Lighting Interiors e-book or Scott's Lighting Video series.
The YN-560-III that was introduced in January of 2013 is a slight refinement of the YN-560-II that has a built-in 2.4Ghz trigger compatible with the RF602/603 triggers. That is, when you are using Scott's manual flash system you need to trigger at least one flash wirelessly if you are going to get the flash off your camera and have one flash fire other flashes optically. What I like about the YN-560-III is it eliminates parts and batteries because it has a RF602/603 receiver built-in to it.
So the complete setup would be:
For those just starting out with Scott's manual flash system the YN-560-III and an RF603/603 make a great first flash. It gets your flash off the camera, it triggers wirelessly without spending a fortune on triggers, and it minimizes parts and batteries. Then as you learn Scott's system and need to acquire more flashes you can acquire, SB-80dxs, or YN-560-IIs or YN-560-IIIs any of which can be optically triggered by the first YN-560-III. If you have multiple YN-560-IIIs you can trigger them all with the RF602/603 trigger in your hot shoe.
It's worth pointing out that at 2014 prices you can get 2 YN-560-IIIs and a set of RF602/603 triggers for the same price as 1 used SB-80Dx. Scott and David Hobby have been promoting the SB-80Dx for years and the price keeps going up and up. There are currently 2 available from KEH, one for $189 and one for $194.
I can attest to the build quality and reliability of the YN-560-IIs and -IIIs because I have 3 of the -IIIs and 2 of the -IIs. I never have any reliability issues with mine. The touch and feel of the Yongnuo's is very similar to my obscenely expensive Canon 580EX which I haven't used since I met Scott.