Namecoin [1] was an early fork of bitcoin, that did blockchain based DNS, with the ideas being actively discussed by Satoshi Nakamoto [2].

That deals with DNS (though how much has it been used?), but what about the layers of the stack?

[1] https://en.wikipedia.org/wiki/Namecoin

[2] https://bitcointalk.org/index.php?topic=1790.222