The title says it all. The web site has a large listing of Vatican documents, including the type (Exhoration, Decree, Letter, etc.), the topics (Eucharist, Liturgy, Mary, etc.), date of publication, author (whether a Pope or a specific office of the Vatican), and sometimes online translations.
It is immensely helpful.
(Catholic Culture also has a large library: beta1.catholicculture.org/library/.)