For a wonderful source of information on Catholic theology, philosophy, and history, head on over to the Institute of Catholic Culture. The website consists of FREE talks given by Catholic professors, speakers, and clergy.
While there are a number of talks I found superb, I highly recommend any talk by Dr. William Marshner, who is a convert from Lutheranism. While he attended the Lutheran college at Gettysburg (the site of the great 1863 Civil War battle), he eventually entered the Church, recieved a doctorate, and has been teaching at Christendom College since 1977.
His recentmost series is called The Council of Trent, the Reformation & the Mass. I highly recommend downloading the second talk which consists of Trent's teaching on the sacrificial character of the Mass. Dr. Marshner has as good a sense for Biblical exegesis as he does for history. All of his talks are well worth listening to!