Last year I saw a really cool home-build machine that was used for mounting SMT components to PCBs. A small manual pick and place machine was cool at the time but I had no real use for it. But now with recent projects forcing me to use these tiny components, I really needed a better way and this popped into my mind as a cheap and pretty straight forward solution.
It’s just in the planning phase at the moment as I’m really only doing this with the spare time that I don’t have much of, but the concept is coming along nicely.
Check out the blog of the man who invented this neat little contraption and made it open source for everyone to make their own versions of it.
Downing's Basement 
I find rotating the part to align with its pads on the PCB to be the most challenging part in hand-placing. Not moving it to an XY point on the board per se but moving it and rotating in coordination so that the center of the part is still in the center of the symmetry of the pads and the legs are aligned with the pads. So, some sort of a lazy Susan – type device in between the longer tracks would be essential for this to work well. To be able to rotate a (arbitrary shape) PCB would would place further limits on the physical size of the PCB you can handle, so spread those apart as far as you can.
I’ve seen that project, and it is pretty cool but I could not help thinking that the maker did all the hard parts – the body, the linear bearings etc. but left out what looks like a relatively easy addition at this point – a couple of steppers with pulleys and belts.cables and a CNC control for the actual, well, control of the thing…
I made one of the ones you have shown here and loved it. Then I found this one online (http://www.steadyhandspnp.com/) that is smaller and quite a bit smoother. For the work I do, there’s no sense making it fully CNC… I’m just doing one and two prototyping boards so it’ll take me more time to program than to just assemble.