Have you heard of the Post a Patch project? People from all over the world knit or crochet squares which are then sent to the lovely Iona in Australia who makes them into blankets and donates them to charity. A wonderful initiative, and a great use for all those oddments of yarn you have lying around. Visit http://www.post-a-patch.blogspot.com.au/ for all the details,or you can follow Post A Patch on Twitter.
If you have a little spare time and yarn, I urge you to get involoved too. It feels so rewarding - it's lovely to know that the blankets will be given to people who really need them (you can see which charities are currently being helped by visiting the website). Full details of how to make the squares and the address to post them to can be found here.
If you know of any similar projects, particularly in the UK, I'd love to hear about them.