15 Materials - Blender materials based on specs provided by Christopher Nichols' Understanding Metalness on chaos.com.
47 Materials - Blender materials based on specs provided by Jarrod Hasenjäger's Material Studies: Metals.
52 Materials - Harvested from tutorials and sample files, attributed in the Material names.
908 Materials - A port of the Materials Library files that shipped with the Blender 2.7.2-compatible version of the add-on, but which are missing from the version that ships with current Blender.
Alternately, Adamantite Machine has done the same thing with their Blender Asset Pack. Great minds… amirite?
1 Collection / 242 Materials / 3 Lights / 75 Node Groups / 20 Worlds - Collected Blender materials, node groups, objects and worlds I've made from tips and tutorials.