Wherefore Art Thou, Hanukkah?

I'll try to answer your question to the best of my abilities, but since Hanukkah is a Jewish celebration not observed by most Christians, you might also poll the opinions of some Jewish sources.

Hanukkah is the annual celebration of the rededication of the second temple (built in the days of Ezra-Nehemiah). During the reign of the Syro-Grecian emperor Antiochus, the Jews were under persecution, and the temple was defiled. In 165 B.C., however, the Maccabean revolt freed Jerusalem and the temple from Syro-Grecian control. The temple then needed to be rededicated.

Part of the rededication ceremony required the use of special lamps which were to burn for eight days, but the defilement of the temple had left only enough unspoiled lamp oil to last one day. As tradition has it, that oil miraculously lasted the full eight days. Hanukkah celebrates the rededication, and remembers the miracle of the oil.

Unlike such holidays as Yom Kippur and Passover, the annual Hanukkah celebration is not a God-ordained celebration. Rather, it is a simple memorial celebration observed by the Jews, much like Christmas is a simple memorial observed by Christians. Hanukkah, though, does not match Christmas in its religious significance. In fact, it is a relatively minor holiday to the Jews. It's popularity is probably due more to its timing (the Christmas season) than to its religious importance.