This is a list of visualization resources that are general and do not fit nicely within any of the other buckets of top resources.
D3.js Gallery. Tutorial. The de facto language for creating beautiful, interactive and dynamic visualizations. This is a great gallery of beautiful plots created using the D3 library, from which you can also learn how to use it. There are great tutorials online to learn how to use D3, as well as a package in R for it.
Vega. Gallery. Tutorial. Vega gives you the ability to create beautiful visualizations using clearly laid-out and meaningful JSON files.