Over the past few years, the Congregation for the Clergy has quietly worked to make available a large collection of texts. It is possible to obtain a CD with these texts on or to download the whole collection to your hard drive. The collection is updated from time to time and there is a tool to update the collection on your hard drive.
The collection includes the bible, commentaries from the Fathers, various other patristic and spiritual texts, and various catechisms including the Catechism of the Catholic Church, the Catechism of the Council of Trent, the Catechism of St Pius X and the Baltimore Catechism.
The Liturgical section has the Missal of 2002 and the Missal of 1957. These are useful since although the old Missal is available on pdf, this version is a little easier to navigate through and the text a little easier to grab.
With the bible, there is a good tool provided in the "comment" button which changes the sidebar to give links from a chosen section to various patristic and magisterial texts.