Today is the Tenth of Teveth, a fast day commemorating, primarily, the siege of Jerusalem by Nebuchadnezzar. (It also mourns the passing of Ezra the Scribe and the translation of the Torah into Greek.)
Audio shiurim can be found at YUTorah.org:
Rabbi Meir Goldwicht (Hebrew)
Rabbi Mordechai Willig
Point of interest: Along the way, Rabbi Willig manages to discuss Christmas and Jewish attitudes towards Christian society.