Comment by trevz

A couple of thoughts, off the top of my head:

Programming languages:

  - python (for general purpose programming)
  - R (for statistics)
  - bash (for cleaning up files)
  - SQL (for querying databases)

Tools:

  - Pandas (for Python)
  - RStudio (for R)
  - Postgres (for SQL)
  - Excel (the format your customers will want ;-) )

Libraries:

  - SciPy (ecosystem for scientific computing)
  - NLTK (for natural language)
  - D3.js (for rendering results online)