If you have read Mark before you might have noticed that it ends abruptly. To be more specific, it ends at verse 8; the two Mary's go to anoint Jesus' body; when they get there, the stone in front of the tomb has been moved and a man appears telling them not to be afraid. Judging by the women's reaction (they were literally trembling like they saw a ghost), it was probably an Angel.
The chapter (and book of Mark) ends with the two Mary's trembling, and telling no one. That's it. No appearing to others--not even an actual Jesus appearing.
Not the Mark you heard in Sunday school? That's because "some" manuscripts took things a bit further. In fact, if you have a Bible then open it to Mark 16; chances are, you'll see some little reference in the chapter mentioning that the earliest manuscripts don't contain verse 9 to 20.
So what gives? If you believe that verse 9 to 20 were there all along, then your good! Why mess with a good thing? Sure, pretty much every scholar would disagree with you, but who cares, right? Just keep believing, because it seems to be making you happy.
But what if you want to believe it's not there? Why would the Gospel end so abruptly? You really have to consider the point of the book to answer that. The other Gospels hit it hard that Jesus rose from the dead--they wanted people to know it and tell it. Mark isn't so much about the miracle as much as how followers should behave. Mark emphasized discipleship; unlike other Gospels, Mark doesn't even bother telling about Jesus' youth--he gets right to the ministry of Jesus, and how, as a believer one is supposed to live.
To some, the greatest thing about Jesus was that he came back; for Mark, the greatest thing is what Jesus gave while he was here.
Also, keep in mind that just because the Gospel bares Mark's name doesn't mean Mark, the disciple wrote it; many scholars attribute the book to a follower of Mark's teaching. If that is true, then it makes sense that they would emphasize discipleship over the resurrection because that's what his ministry/teaching was all about. To tell someone you belonged to a church that Mark started meant that you held discipleship pretty highly.