Chris Albon has made a comprehensive list of tutorials in Python and R.
A guide that helps you pick the right & relevant viz for your data.
Browser extension for making charts.
Network analysis made easy peasy.
A simple but powerful chart maker in the cloud.
A shortcut to making D3 charts.
Visualize data on SVG maps.
A D3.js add-on for simplifying code.
Build vector graphics from scratch.