Required Textbooks

D3

D3.js is a JavaScript library for manipulating documents based on data. D3 helps you bring data to life using HTML, SVG, and CSS.

Official D3 Site
Official D3 API reference (version 4)
Official D3 API reference (version 3.x)
D3 Tutorial by Scott Murray (D3 version 3)
Jerome Cukier’s D3 Cheat Sheet

Web Development

Courseduck Javascript - Listing of best online JS courses WebStorm by JetBrains - Smart JavaScript IDE (free for students)
Eloquent Javascript Book
DevDocs, Mozilla Developer Network - Unified documentations on major web technologies
Github (Git repository hosting service) - Version control system for software development (free private repositories for students)

Tableau

Tableau Software is a tool that lets you create interactive data visualizations. (free for students)

Data Sources

Data.gov
Census.gov
Dataverse Network
Climate Data Sources
Climate Station Records
CDC Data (Disease Control and Prevention)
World Bank Catalog
Free SVG Maps
UK Office for National Statistics
StateMaster
Quandl

Web Sites & Blogs

Flowing Data
Visual Complexity
Guardian DataBlog
The Upshot

Other Software Toolkits

Plot.ly
Wolfram Mathematica
Prefuse (Java)