It seems that applause is becoming more widespread in our churches. According to Cardinal Ratzinger, now Pope Benedict, in his book The Spirit of the Liturgy, "when applause breaks out at Mass, it becomes ecclesiastical entertainment."
It seems that applause is solely for the music ministry. As much as I appreciate the music, I feel it is inappropriate to applaud. This is the Holy Sacrifice of the Mass, not entertainment. It is for the glory of God, after all.
It might be more appropriate to approach the musicians after Mass and extend your appreciation of their gifts, as well as thanking the ushers, the altar servers and priest for their gifts as well.