I dabbled in web-based mapping a couple years ago and found the tech stack to be really quite polished. Starting from a database of features from e.g. OpenStreetMap hosted in a Postgres-based PostGIS map server, and geographical boundaries via special shape files, you can write XML files representing the features you wish to see on each layer of the map (using SQL queries intended for PostGIS), and CSS-like style files representing how the features should look. You then set up a tile server (Apache or nginx or whatever) that generates tiles on demand and performs caching. Finally you use a JavaScript library to provide the "slippy map" that users can drag around.
All of these layers of the tech stack have FOSS implementations; indeed most of the most widely used ones are FOSS. And then there's QGIS (also FOSS) to do most of this in a similar fashion, but offline.
As merely a dabbler having a bit of fun, it's rather excellent I must say. It would be interesting to hear from anyone working in this field professionally as to how the FOSS tools measure up.
All of these layers of the tech stack have FOSS implementations; indeed most of the most widely used ones are FOSS. And then there's QGIS (also FOSS) to do most of this in a similar fashion, but offline.
As merely a dabbler having a bit of fun, it's rather excellent I must say. It would be interesting to hear from anyone working in this field professionally as to how the FOSS tools measure up.