I've posted about it before, but I'll always love this one:
"I tell everybody a little parable about the teaspoon brigades. Imagine a big seesaw. One end of the seesaw is on the ground because it has a big basket half full of rocks in it. The other end of the seesaw is up in the air because it's got a basket one-quarter full of sand. Some of us have teaspoons, and we are trying to fill it up. Most people are scoffing at us. They say, 'People like you have been trying for thousands of years, but it is leaking out of that basket as fast as you are putting it in. Our answer is that we are getting more people with teaspoons every day. And we believe that one of these days or years -- who knows� that basket of sand is going to be so full that you are going to see that whole seesaw going zoop! in the other direction. Then people are going to say, 'How did it happen so suddenly?' And we answer, 'Us and our little teaspoons over thousands of years.'
-'Uncle' Pete Seeger