The GeoNames geographical database covers all countries and contains over eleven million placenames that are available for download free of charge.
Web services data API: http://www.geonames.org/export/ws-overview.html
Poke around in there, you'll find some interesting things, like earthquakes, geolocated datasets (eg, nearby Wikipedia pages), Open Streetmap interface. They might even be useful.
A site that lets you create map layers on top of Open Streetmap and make them shareable and embeddable. You can upload geodata or sketch in the data you want.
Source code: https://github.com/umap-project/umap
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