https://openmaptiles.org (only map tiles)
https://stadiamaps.com (map tiles, static maps & routing)
https://www.thunderforest.com (only maps)
https://geocoder.opencagedata.com (only geocoding)
https://geocode.earth (only geocoding)
A laundry listing: https://switch2osm.org/providers/Tile providers are very thankful for the excellent rendering libraries built by Mapbox, Mapzen, and the Leaflet project. Most maps either use Leaflet.js or MapBox GL JS (open source) for their rendering agent, now that Mapzen is defunct (although their rendering library, tangrams, is now open source).
(I am a co-founder of Stadia Maps.)