I keep thinking about saying this, but don't really have a proper conclusion. I think the time has come to say it anyway…
I often think that the apostle known as 'Doubting' Thomas gets an undeservedly bad press. If we look at the relevant parts of the gospel, we see that, actually, he was absent for Jesus' first appearance in the presence of the disciples - really, in saying he won't believe Jesus has been raised form the dead unless he sees and touches Jesus for himself, he isn't wanting or expecting anything the others hadn't already experienced.
On the evening of that first day of the week, when the disciples were together, with the doors locked for fear of the Jewish leaders, Jesus came and stood among them and said, “Peace be with you!” After he said this, he showed them his hands and side. The disciples were overjoyed when they saw the Lord.
Again Jesus said, “Peace be with you! As the Father has sent me, I am sending you.” And with that he breathed on them and said, “Receive the Holy Spirit. If you forgive anyone’s sins, their sins are forgiven; if you do not forgive them, they are not forgiven.”
Now Thomas (also known as Didymus), one of the Twelve, was not with the disciples when Jesus came. So the other disciples told him, “We have seen the Lord!”
But he said to them, “Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe.”
A week later his disciples were in the house again, and Thomas was with them. Though the doors were locked, Jesus came and stood among them and said, “Peace be with you!” Then he said to Thomas, “Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe.”
Thomas said to him, “My Lord and my God!”
Then Jesus told him, “Because you have seen me, you have believed; blessed are those who have not seen and yet have believed.” John 20: 19-29
The passage above reads almost as if, in the first instance, he thinks the other disciples are making him the butt of a particularly inappropriate joke, and he's simply reacting to that. So I really don't see why he deserves the 'doubting' epithet.
I don't believe it's wrong to doubt though - it shows that one's faith is alive and well, and that one is continuing to think and seek after truth. Doubt isn't the same as unbelief, which I think is an absence of faith. Personally, I question all sorts of things, almost all the time. Questioning, and thinking helps me to make sense of my faith, and to relate it to the world around me - so it's relevant and up-to-date, rather than being stuck in the past.