This tool allows you to easily visualize one or more choropleth maps on your web browser, and should work for nearly any geographic scope. After loading your input files, you can click on + to add the choropleth map corresponding to a specific variable. Note that you can display multiple maps, in case you want to visualize two or more variables at the same time. If you no longer want to display one of the maps, you can click on - to delete it.
The maps are zoomable with the scroll of a mouse, and can be moved by drag-and-drop. If you provide data for multiple time periods, you can play a video that shows the evolution of the map(s) over time.

Input files
You need to provide three files: Sample input files, instructions and programs to prepare the input files from standard formats can be found here.

Web browser and security
While I expect the program to work for any modern web browser, it appears to be fastest with Google Chrome, and other web browsers may be too slow for a nice user experience if you have large data.
The input files are simply loaded within your web browser and are not uploaded to the server. Even though your web browser may signal the page as "Not Secure", your data is not being shared, it simply stays on your local computer.