When the Day of Pentecost came, they were all together in one place. What does that tell us? It tells us that they weren't scattered about, each doing their own thing.
Peter didn't have his group of followers, as opposed to Matthew having his. Thomas hadn't started Doubters Anonymous, and James and John hadn't yet created the five simple steps to sitting at the right hand of Jesus. They were all together, in one place, and the spirit of God moved upon them.
We are so caught up in the culture of American individualism that we have a difficult time grasping the significance of how the day of Pentecost began. Before there was a rushing sound, before there were tongues of fire and languages, and before Peter's powerful sermon was given and converts were made, the people were together, in one place, in one prayer.
We have a harder time being present to one another than being present to God - but can we truly be present to God if we are not present to one another?