I remember that on my old personal website in the past, exactly in this period, to celebrate Christmas days I always placed a litlte Javascript on my HTML body to draw a snow effect on the main page of the site.
Todd Bleeker has done exactly the same for Sharepoint in a more elegant manner: he has embedded a JavaScript code in a content editor web part that will draw the famous snow falling effects on your SharePoint site.
To obtain this nice effect, just save the snow.dwp locally and import it onto the Web Part page. You're ready for snowing... 
So simple and so nice... thanks Todd, and Marry Christmas! 