There are three versions of Halloween historically.
The first is the Celtic festival of Samhain, which celebrates the night when the distance between the world of the living and the world of the spirits is at its weakest point. In this version of Halloween, modern day witches and druids (Wiccans) build huge bonfires to celebrate the spirits or their ancestors, fairies, etc. There are some definite demonic aspects to these festivals, and you should absolutely not participate in these types of events.
The second version comes from the Catholic celebration of Hallow's Eve, the day that comes before All Saint's Day (Nov 1st) where Catholic believers celebrate the saints of God. If you can find a Catholic celebrating such an event, I say go for it since Catholic believers are our brothers and sisters in Christ.
The third version is the modern version, which people dress up for fun and give out and/or receive candy. For most people this holiday has zero religious or demonic connotations. Most people just dress up to have fun while hanging out with friends (and getting free candy to boot!). While I would agree that there are some costumes that a Christian should not wear, there is nothing evil about this holiday that I can see from the Bible.
Jappel (and others for sure), if dressing up for Halloween or celebrating it bothers your conscience, you should absolutely not celebrate it. The church I grew up in felt that way. We had harvest festivals instead. I, myself, did dress up occasionally and hang out with my friends. I did the same with my kids. As far as I can tell, there have been no negative side affects from the experience on either side (unless you count my kids getting mad for me taking a tithe of their candy in the form of all of their Sweet Tarts).
Every believer has to decide what his or her non-negotiables are from the Bible. For me, the celebration of Halloween is not one of them. If the celebration of the holiday came between me and Jesus, I would drop it like a hot rock. Since it does not, I'll hold to the standard of Romans 14, which calls for freedom on the negotiables as long as it does not cause another to stumble.
I'm pretty sure the purpose of Song of Songs is to make people feel uncomfortable in youth group.
That being said, it seems to me to be a collection of love poems with no true theological significance other than to show that love between a man and woman in marriage need not be a passionless, baby-making experience. Other interpretations, such as applying to Jesus and the Church, seems to read stuff into the text that is not really there.
I was watching a documentary on naval warfare last week. One of the challenges of pre-radar naval warfare is the limitations of the curvature of the earth. If I recall correctly, the maximum viewing distance in any direction on the ocean is 30 KM. This small distance offered very little response time upon spotting an enemy.