If you would like to try out the snow script on your own site (or any other site for that matter), use this bookmarklet:
Snow Fall
Drag it to your bookmark bar, add it to your bookmarks list, or however you add bookmarks, then when you visit the page you want to add snow to, click the bookmark. The snowfall.js file will be loaded and snow will start falling on the page.
Don't worry, the effect is only temporary, refresh the page to get rid of the snow again!