In time a huge list of useful tools and ressources has accumulated. I have not used all of them, but most. I try to give an indication if something is free & open source.
# Desktop Software
To create a meaningful data visualization certain software is needed. Depending on the task they are categorized in GIS software, map making or design related. Have fun discovering something new!
# Web Development
Open data portals, web maps, diagramm and data visualization is trending in web development. Here is a list of tools to support you in your processing and visualizing.
# Other Useful tools to Help with Small Tasks
Sometimes things need to be done, that has not much to do with cartography, map making or design, but proven to be useful none the less. In this list are these helpers collected to maybe help you with something.