Just found this great script on this site that lets you add a snow effect to your forums, its great to add on Christmas Day. The great thing about this script is that its free and you don't have to keep it just for snowing, you could add leaves, and pumpkins (Halloween) for just about any graphic you want, credit goes to Sasa Skevin for creating such a good script.
You can see a DEMO HERE on the Dynamicdrive homepage, its a great site with loads of scripts you could integrate within your forums.
Enjoy,
UKBusinessLive
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I have moved and edited this script for easy use by the members. I have added instructions and added the script to a file which is loaded.
This code is a free source from DynamicDrive.com. Users are NOT allowed to remove the copyrights.
Thanks,
-Roms
***********Update*****************
Just added a Valentine 10 x Hearts Collection, so you can use this as a treat on Valentines day