Anyway I did have a lovely time at @edinburghjs.org (and clearly should've gone to the pub with everyone instead of sneaking out!)

Leaflet.js is a JS library that can be used with any map tiles - such as those from OpenStreetMap - to add pins and simple interactions. It's pretty straightforward to set up, even for a beginner dev. It's what I chose - together with gorgeous base maps from Stadia Maps, based on OSM data.

(I skipped a few as I'm looking for a way to pin engagements on a map, rather than planning routes - hi TomTom!)

MapBox is a contender - recommended for customisability, also not the cheapest.

Google Maps is Google Maps. Tons of features, tons of data, can get pricy if you're not careful.