CSS (+ some Javascript) framework, implementing Google's material design for static web pages.
Can be used for plain websites without requiring a full blown Javascript framework, unlike the (also excellent) Polymer paper elements Show archive.org snapshot , or Angular material Show archive.org snapshot .
I would recommend against using it at this stage, for a couple of reasons:
It is much less complete than you might expect from a CSS framework. There is little support for forms elements, for example.
Markup is somewhat akward.
It does not play nicely with livereload and will constantly scroll the page to the top.
Using it together with a JavaScript framework requires some care, because you constantly need to "upgrade" elements with MDL.
Materializecss Show archive.org snapshot
Material-ui Show archive.org snapshot
Material Design for Bootstrap Show archive.org snapshot (note that this is incomplete, and free only for non-commercial projects)
"Paper" Bootstrap theme by Bootswatch Show archive.org snapshot (we also have a card about it)