MJ's Data Journalism Academy
This site, created by data journalist MaryJo Webster, contains materials that she uses to teach basic data journalism concepts to reporters, and occasionally editors. There's a mix of videos, exercises, tipsheets and reading materials to introduce you to both how to work with data, but also some of the bigger concepts you also need to learn, like finding and requesting data and dealing with problems in your data and incorporating this work into a beat. The basic exercises teach you how to work with data in Microsoft Excel, however the primary goal is to help you understand how to work with data, in general, regardless of the tool.
If you're a beginner, I've laid out below a recommended order for working through this site.
Questions? Contact MaryJo Webster. If you like my work, please consider making a donation via PayPal. Thank you!