Data Engines

Data Engines.  A reminder of this topic, which I had forgotten about.  You want to perform some analytic process, but where is the required data?  Often a big issue.  A list of examples.  Including Quandl, a new one in the mix.   " ... A while back, I wrote for some time on this blog about 'data engines' - search engines dedicated to online (statistical) data sets. ...  "  writes Matthew Hurst.