I think, more than anything about Judaism that fascinates me to no end is the question of origins. Naturally this includes the big questions about the universe, the Jewish people, the Torah and so on - but also the relatively smaller questions. Why was pork forbidden as an unclean animal? What is tzitzit? Why circumcision? Why Shabbos? Who wrote this or that prayer and what does it mean? Why do we fast on Ta'anit Esther? Why don't we cut our hair during Sfira?
What is often most fascinating about all this is the very different answers you may get from traditional sources as compared to academic scholarship, assuming the origins aren't lost in the sands of time. As I brought the question up recently on XGH's blog - why is Chanukah eight days long? The Talmud says because the oil miraculously lasted that long. What says historical sources like 2 Maccabees? Because they were celebrating Succos in Kislev. Back in Tishrei when they were at war, the Temple was impure and they couldn't do it properly so they translated the eight days of Succos + Shmini Atzeret into Kislev and established a holiday. Understanding the true origins of a practice usually makes it that much more meaningful.
Anyway, I was wondering recently about the origins of the feather, wooden spoon, and candle deal that is traditionally used for bedikat chametz. I figure it's probably kabbalistic, but I haven't been able to track it down. What are the objects supposed to signify? A gold star to whomever can give me the answer.