So, I like Christmas music, and I like free stuff. It is only natural for me to look for free Christmas music downloads. For example, there's those Christmas Messages from Max Lucado.
As for music, howver, here's what I've found so far:
Feels Like Christmas has Christmas music, stories, coloring books... very nice.
Songs of Praise has artist-contributed music. They only ask that, if you use them commercially or in church, to help them make some money back by reporting to CCLI. Mostly instrumental, but that was what I wanted, anyway.
Gargage Band consists of indie bands, some of which are good and some rather pedestrian. Anyway, if you look for songs in the sub-genres 'Seasonal/Holiday' 'Christmas' you'll find a significant amount of music. For example, I found a version of 'O Come, O Come Emmanuel' I really liked.