Luke 7

19 This question most likely reflects the despair that John felt in prison. He anticipated Jesus conquering the Roman Empire and freeing him from his cell. He had forgotten that he was the one who witnessed the descension of the Holy Spirit on Jesus, which was the sign he was to look for when he saw the Messiah.

Some have also suggested that the question was meant to direct his own disciples to Jesus. This is certainly possible. If Jesus was the one they were waiting for, then John's disciples should be following Jesus.

22 No one had displayed as much power as Jesus did. The miracles He did were ample evidence that He was the Messiah. Even more importantly, the Good News of the Kingdom of God was being preached to the spiritually poor. Jesus had come to prepare people spiritually for the time when He would come to establish His kingdom.
23 Many people were offended by Jesus because He did not meet their unfounded expectations of what the Messiah "should" be. What they could not see was that Jesus exceeded their limited expectations. The eternal salvation that Jesus brought was far more important than the immediate destruction of the Roman Empire. Jesus will one day destroy all evil, but until then, Christians can savor the hope that Jesus brings into our lives.
24 Whether this answer was clear to John's disciples or not, we do not know. They left Jesus and reported to John.

Jesus then discusses John's ministry to those people who were following Him.

26 John the Baptist was neither a lunatic nor a king. He was a prophet, and the people had flocked to him because of their desire to hear a word from God.
27 In fact, John was a special prophet because he prepared the way for Jesus, the Messiah.
28 John had predicted that Jesus would take away the sin of the world, but apparently was deficient in his understanding of what that meant. The question John raised appears to reveal John's lack of faith in Jesus. The fact that John did not follow Jesus may also be an indicator. On the other hand, Jesus may simply be implying that John will not experience the baptism of the Sprit, or the power and hope that comes from faith in Jesus.
44 It was good manners for a host to provide water for the guests to wash their dusty feet with when enter in a home.
45 A kiss was a customary greeting. The woman's kisses showed passionate devotion.
46 Anointing the head would be customary for special guests (priests, prophets, teachers, and other leaders)
47 It was not a question that Simon only needed a little forgiveness, or that he could not receive forgiveness. Simon simply didn't feel that he needed forgiveness for anything. Since he ignored a gift that he desperately needed, he did not feel obligated to be grateful for it.It is apparent that Simon did not honor Jesus as was proper for any guest, much less as the Son of God.
50 Her faith in Jesus' ability to forgive her saved her. Remember that it is not simply faith that saves you, it is what (or better Who) you have faith in.