I use Rails as a portable, light, zero-conf frontend for data exploration. Just create the minimum viable rails app (--api), fill in the database connection, and you get a powerful REPL for exploring + rake to run transformations.
Who would have thought that the “Data Visualization Toolkit” would be about Rails?
Turns out, it’s pretty sweet actually! rails new, g migration, baddaboom. I’ve done this a few times, but usually use chartkick rather than d3 as the book suggests.