On the Feast of the Assumption this past August, Fr. John Zuhlsdorf delivered the sermon for the Sixth Annual Mass of Thanksgiving of Mater Ecclesiae Roman Catholic Church, a mission parish which celebrates the sacraments according to the pre-Vatican II liturgical books. This Mass was celebrated in Camden, NJ's handsome Immaculate Conception Cathedral.
This sermon is a fine discourse on the true meaning of participatio actuosa. Mater Ecclesiae now has the sermon on the parish website. The sound file can be obtained from Fr. Zuhlsdorf's blog, where you can also hear a snipet of the closing hymn. Be sure to check it out.