I've been pondering Rahab and her place in the story of the conquest of Jericho recently.
Since the primary story of the scriptures is about Christ (John 5.39, "Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me") searching for Christ in a given narrative is good. And although it's easy (my wife accuses me of this frequently) to perhaps see too much in the Old Testament stories, Rahab is a significant character, and I think her story tells us something. She's a type or picture to us. The question is what she's a picture of: I'd argue it's the church.
Notice how Rahab and the church are similar.
1. The church is made up of justified sinners. Rahab is specifically noted as not merely a sinner in general, but a prostitute. The only 2 New Testament references to her (Heb. 11.31, and James 2.25 both specifically mention that).
2. The church is saved by the preaching of the word. Joshua (in Joshua 6.17) calls the 2 spies who lodged with Rahab "messengers." I don't have an interlinear in front of me, but I'd bet that the LXX term there is "angelos," messengers, the same word often used in the NT for those preaching the gospel.
3. Rahab and her family are saved by being in their house, which is also a picture of Noah's ark: those inside are saved, those outside are not.
4. Her house is marked with a scarlet thread; we are buried into Christ's death in baptism, and thus marked with a scarlet mark as well.
5. Rahab confesses the faith: "for the LORD your God, he is God in heaven above, and in earth beneath" (Joshua 2.11) A confession is always a response to the preaching of the word of God, and -- per Matt. 16.17 -- such a true confession is never something we have contrived on our own, but it is a gift to us, something revealed to us by God.
6. Finally, Rahab and her family -- all of those found in the place of safety -- are rescued from destruction as they put their trust in God and His mercy.