The blog post is a couple of years old, so it's probably worth noting that PLaneT[1], mentioned by the author, has been superseded by a new Packages[2] system. PLaneT is still operating, however, and libraries hosted there can be installed with raco[3].

[1] http://planet.racket-lang.org/

[2] http://pkgs.racket-lang.org/

[3] http://docs.racket-lang.org/raco/index.html?q=