Beginning with the first Sunday of Advent - November 27, 2011 Catholic churches in the United States will begin using the 3rd edition of the Roman Missal. This translation is the most true to the Latin language, which is the official language of the Church. There will be changes in both the priest's prayers and the responses of the faithful. The links below summarize these changes.
United States Conference of Catholic Bishops web site on the Roman Missal
Changes in the people's parts of the Mass (.pdf Version)
Changes in the priest's parts of the Mass (.pdf Version)
The order of the Mass (pdf)
The order of the Mass annotated with Scripture references (.pdf)