In the UK it's what used to be the Haig Fund, colloquially known as the 'poppy appeal', which is now its official name. I'd encourage everyone in the UK to make sure you seek out someone with a collection tin and 'wear your poppy with pride' as their slogan goes. I see a lot of people walk past veterans collecting for this benevolent fund, and it always appalls me. If you can't get out to donate, you can do it online here:
http://www.poppy.org.uk/
Chock