The Gospel of Mark, the Gospel of Luke, and the Gospel of John go directly from the burial on Good Friday to the empty tomb on Sunday, with nothing about Saturday. (The links are to the specific passages) The Gospel of Matthew has a few words about what happened on Saturday:
The next day, the one after Preparation Day, the chief priests and the Pharisees went to Pilate. “Sir,” they said, “we remember that while he was still alive that deceiver said, ‘After three days I will rise again.’ So give the order for the tomb to be made secure until the third day. Otherwise, his disciples may come and steal the body and tell the people that he has been raised from the dead. This last deception will be worse than the first.”
“Take a guard,” Pilate answered. “Go, make the tomb as secure as you know how.” So they went and made the tomb secure by putting a seal on the stone and posting the guard.
So, what was written about the Saturday was a curious story that must have occurred directly after Jesus’ death.
Saturday must have been the saddest day, I think. On Good Friday there was the intensity that precedes death so often. Appeals to one authority after another, the courage of those who help the dying bear his cross, the cowardice of those who flee. Tearing clothes and bitter tears.
But on Saturday, he was gone. He was in the ground. The movement defeated and the followers scattered. It felt like he was gone forever, like he had been ripped away. I imagine the followers of the Way sat silently.
UPDATE: There is a great book Pat is reading by Borg & Crossan, titled The Last Week. It does a great job of detailing the Jewish traditions that lead to the idea of descending into hell on Saturday. (Which is not really our idea of hell, and descending is probably also not the best translation!) Here is a blogger who handles the matter in a little less detailed matter, but you can read right now rather than after getting a book.