I don't mean this in a "I'm so smart that I rarely hear something entirely new during a homily" way...it's more of a 1)I don't often get to hear a homily uninterrupted, and 2)I read all the time, so I've usually at least come in contact with an idea before.
So, Father preached about the first reading yesterday, from the Acts of the Apostles. The reading talks about how the people had only been baptised in the name of Jesus, and then Peter and John (I think it was John anyway) came and laid hands upon them and the people received the Holy Spirit. Father talked about how the reading discussed two sacraments (baptism and confirmation), and asked us about the different types of baptism discussed in the Bible.
There are three, but at the time of the reading from Acts, they did not yet understand Baptism of the Holy Spirit. So, what are the other two? Well, he explained that there was John's baptism, and then there was the baptism that Jesus commanded (baptise all nations in the name of the Father and of the Son and of the Holy Spirit).
John's baptism was a baptism of repentance. Jesus's baptism in the name of the Father and the Son and the Holy Spirit was different. So the Jews at the point of Acts knew of two baptisms...the baptism of repentance and the baptism that Jesus commanded. Therefore, when the reading said that they had only been baptised in the name of Jesus, it is not saying that they literally were baptised only in the name of Jesus, but instead were baptised the way Jesus commanded, and had not received the baptism of repentance from John.
I just thought the whole concept was very interesting, and not something I had ever contemplated before!