Important Bird Areas are part of The World Database of Key Biodiversity Areas. The terms and conditions of use clearly state that redistribution is not allowed. See the relevant section quoted below:
4. No reposting and/or redistribution
Except as provided in this section 4, all forms of reposting, and any sub-licensing, reselling, or other forms of ...
The Nasa JPL hosts continent-scale mosaic DEMs (with voids corrected), and you can access using the Google Earth Engine API:
I found some promising hits from a Google search for "glacial extent shapefile bering sea," including:
ArcGIS online layer (global extent): Ice extent and coastline at the last glacial maximum
shapefiles of Pleistocene and Wisconsonian glacial extents in Alaska
A number of scientific articles also turned up during that search. If you look at those articles ...
The GFZ Potsdam, a large research institute in Germany, has several groups working on hyperspectral data.
This page http://www.enmap.org/flights.html lists a table with several datasets from Europe, acquired 2011-2014.
Most of the DOI links on that page lead to the library of GFZ Potsdam, which offers a data download service. However, for some reason most ...
If you want to go for Leaflet and offline (Raster) Tiles, you can checkout https://gitlab.com/IvanSanchez/Leaflet.TileLayer.MBTiles
For non-commercial products you can get free map tiles from https://openmaptiles.org/ (sign-up required).
I found several sources of "country centroids."
Country Centroids, from worldmap.harvard.edu, available to download in many formats (Zipped Shapefile, GML 2.0, GML 3.1.1, CSV, Excel, GeoJSON, GeoTIFF, JPEG, PDF, PNG, KML, View in Google Earth). Also available as a web map service. This dataset comes with a lot (80-ish) of attributes.