Design Resources:

Visual Vocabulary (which graph should I use): https://raw.githubusercontent.com/ft-interactive/chart-doctor/master/visual-vocabulary/poster.png
Visualization Galleries (find visualizations on similar topics or just use for general inspiration):

https://reddit.com/r/dataisbeautiful
https://esconfluence.tableau.com/en-us/s/gallery (Tableau notebooks here can be downloaded so you can see how visualizations are created)

Online Design Tools:

Flowchart maker: https://www.draw.io/
Adobe color wheel: https://color.adobe.com/create/color-wheel/
Stylized map maker: https://snazzymaps.com/
SVG maker: https://github.com/SVG-Edit/svgedit
(Illustrator) Practice pen tool: https://bezier.method.ac/

Datasources:

Datasets, tutorials, and data competitions: Kaggle.com
Datasets: https://www.datasciencecentral.com/profiles/blogs/great-github-list-of-public-data-sets
CDC Datasets: https://github.com/cdcepi

Python:

Data Science Toolbox: https://www.kaggle.com/mjbahmani/the-data-scientist-s-toolbox-tutorial
Intro to python : https://overiq.com/python/3.4/intro-to-python/

Unix:

Linux Tutorial: https://linuxjourney.com/
Shell Command Explainer: https://explainshell.com/

Programming Utilities:

Regex Tester: regex101.com
Markdown Editor: https://jbt.github.io/markdown-editor/

Databases:

SQL Cheat Sheet: http://files.zeroturnaround.com/pdf/zt_sql_cheat_sheet.pdf
SQL Tutorial: http://sqlzoo.net/
Python SQL Toolkit and ORM: https://github.com/zzzeek/sqlalchemy

Helpful Google Searches:

"site:github.com Awesome [Blank]" : Github awesome "blank" pages contain curated list of resources related to your topic

ex: https://github.com/mathsyouth/awesome-text-summarization , https://github.com/vinta/awesome-python

Aggregate list of some of these resources: https://github.com/sindresorhus/awesome

"site:github.com [Blank] cheat sheet" : Quick reference material for the searched subject

ex: https://github.com/ehmatthes/pcc/tree/master/cheat_sheets

Other:

Tutorials: https://www.lynda.com/ (free for Virginia Tech studnets)
Curated programming resources: https://github.com/Michael0x2a/curated-programming-resources/blob/master/resources.md
Academic Citation Tool: https://harzing.com/resources/publish-or-perish

Interesting Visualizations:

Spotify visualizations: http://www.rcharlie.net/sentify/
Google Trend Data: https://trends.google.com/trends/?geo=US