Will Norris

Adds Javascript snow effect to your blog, thanks to <a href="http://www.schillmania.com/projects/snowstorm/" rel="nofollow ugc">Scott Schiller</a>. This is the same effect available on WordPress.com blogs.

Snow Storm

Adds Javascript snow effect to your blog, thanks to Scott Schiller.  This is the same effect available on WordPress.com blogs.

veradeveloper

Animated snow plugin for your website.
Documentation 
To change global settings, go to “Settings” -> “Snow Time”.

Snow Time

Very simple in use and nicely for christmas time.

Snow Storm vs Snow Time