I have mentioned the sermons of Fr. George Passias before on this blog, specifically the series on The Life of the Theotokos. I was recently emailed an excellent site where many of his sermons (some only a few minutes, others hours long) are posted.

I highly encourage you to check some of them out. There is a 3 minute one entitled, "How do you know it's Christmas?" that is great.

http://www.saintspyridon.net/sermons/sermons.html