The JVC (Jewish Volunteer Connection) in Baltimore (ok, Pikesville, if you want to get technical) organizes a Mitzvah Day project for Christmas Day each year.
This year's project is hats and scarves to be given as part of a Winter Survival Kit to the homeless on December 25th.
No, you don't have to be Jewish to contribute. (*g* Hey, I've got yarn that was dying to find a new project home - and not being wild about the color combo myself, I figure it'll go well in scarves, and hopefully the people who get them *will* like the colors, especially as I know a couple people who do like the brown-blue combo now)
For more info, the webpage with general info is at
http://jvcbaltimore.org/jvc-programs/community-mitzvah-day/