Fromper,
What a fantastic idea! We've got a box here at work, and I don't know why I didn't think of a chess set. So count me in and let me give my wholehearted second to your recommendation.
Give the gift of chess to unlucky kids
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COOL! My dad manages a dollar general so we do this alot. I never thought about a chess set before!
Very good idea!
Another good idea is Childs Play Charity.
"Since 2003, over 100,000 gamers worldwide have banded together through Child’s Play, a community based charity grown and nurtured from the game culture and industry. Over two million dollars in donations of toys, games, books and cash for sick kids in children’s hospitals across North America and the world have been collected since our inception.
This year, we have continued expanding across the country and the globe. With over 45 partner hospitals and more arriving every month, you can be sure to find one from the map above that needs your help! You can choose to purchase requested items from their online retailer wish lists, or make a cash donation that helps out Child’s Play hospitals everywhere. Any items purchased through Amazon will be shipped directly to your hospital of choice, so please be sure to select their shipping address rather than your own.
When gamers give back, it makes a difference!"
As a gamer, I always liked this charity. 
We have a "Toys for Tots" collection bin at my office, where they are collecting donations of toys to give as Christmas presents to underpriviledged children. I usually throw in a chess set every year, so I figured I'd post here to encourage everyone else to do the same. Most toy stores have donation bins this time of year for this sort of thing, so you should be able to find one.
You can get a cheap chess set for $3 at most stores. Or if you want to make sure the kid who receives it has an easy time learning the game and really learns the rules correctly (including stuff like castling and en pessant, which are often left out of basic instructions), you can spend a little more to donate this product:
http://www.kidzworld.com/article/5931-no-stress-chess-review
My nephews learned the game from that No Stress Chess game last year at 5 and 7 years old, and they love it. The cards make it easy for them to remember how to move each piece, and the board is labeled on one side with the starting locations of the pieces. The other side of the board is unlabeled, and the instructions with the game go over ALL the rules for normal chess, including some basic strategy tips. There are even transition type games, where instead of picking one card every turn, you get a hand of 3 or 5 cards, so they work their way up to choosing which piece to move by themselves. I highly recommend this product as a great way to teach new players of any age. And no, I don't work for the company or anything like that.
--Fromper