The 99 Most Essential Christmas Masterpieces
It turns out that if you want classical music, Amazon is happy to provide it in bulk for very little money. I'm sure a lot of these recordings - or at least similar ones - are available for free, but this saves me the time of having to scour the internet for options.
I'm not sure the price will last, but I actually got this for $1.99, meaning I paid about two cents a song. The recordings aren't fantastic, but then neither is my sound system. The sheer number of pieces means I can put this on random and listen for hours on end without hearing the same songs over and over again.
Highly recommended if you want a collection of holiday music without the hassle that goes along with putting it together yourself.