I was taught that charity and charitable acts were done privately and not for applause, and that's a lesson that sticks mostly. It just feels right.
I agree with that. It's been tempting to go around blaring to everyone posting links about where and how to donate, how much, when and to whom I've donated, but I just think it comes off as crass. It's better to spread the word and let people's conscience guide them than try to use your own donation as a measuring stick. Some may be able to donate 10,000 dollars/pounds/euros/whatevers, some 100, others can afford 10. It's really about doing it for the sake of doing it, not to show off, not to make others feel bad, but to help someone to whom your "spare change" whether it's a million bucks or 5, can make a world of a difference.
Some people can't afford to give money at all, but can and do help in other ways (volunteering time and technical skills, for instance is a huge help for many humanitarian and other social organizations), it's all good.