Clause or Claus? If everything says Clause, you have a lot of correcting to do... It's Santa Claus!
I know you won't be able to do this, ABall, but I thought I'd share how we did it... My kinders would write letters to Santa, then we'd take them to the office and the secretaries would run them through the machine to put postage on them and we'd place them in the mailbox. The gifted class picked them up and answered the letters!
Search Google for letters from Santa, and you'll find several that will send a letter to your child for a fee.
As for letter writing projects for schools - Here is one you can keep in mind for next year, but registration for this year is closed:
http://www.globalschoolnet.org/programs/santa/
Here is another idea where HS students write letters for $2. It doesn't indicate a YEAR, but it is linked from the school's home page so it should be current:
http://www.harlan.k12.ky.us/chs/letters_from_santa.html