ScreenSavers EZskins' Christmas section has a choice of over 100 free Christmas screensavers.
Content here is updated daily.
This site also has a very extensive selection of Christmas desktop themes, Winamp skins and much more. Here's a fun, free online game that features Santa surfing down a mountain slope on his rump. Requires the free Macromedia Shockwave plugin. This site offers a festive, fun collection of free Christmas-themed digital greeting cards. Here's a handy resource that offers hundreds of free catalogs and is well organized so that you can easily choose from among dozens of categories.