One of the best ideas I've seen (and signed up for) recently is participation in the http://www.colalife.org/ initiative.
Around the world, children die every day from dehydration that results from preventable diseases such as diarrhoea.
As stated on their website:
Cola Life's idea is that Coca Cola use their distribution channels (which are amazing in developing countries) to distribute 'social products', such as oral rehydration salts, to the people who need them desperately.
To find out more: http://www.colalife.org/
