How much should we give?

Following the horrific events in Japan this week, I realized that I have neglected something crucial: I haven't allocated any funds in my budget for charitable giving.

I thought about it this morning on the way to work. It was raining and I remembered a parable from the bible (bear with me, I promise this won't turn into a religious diatribe!)
It was Luke 21: 1-4, the parable of the widow's offering. Please, keep reading even if you think the bible's a load of crap. I promise this will be interesting:

"As Jesus looked up, he saw the rich putting their gifts into the temple treasury. He also saw a poor widow put in two very small copper coins. “Truly I tell you,” he said, “this poor widow has put in more than all the others. All these people gave their gifts out of their wealth; but she out of her poverty put in all she had to live on.”

This made a big impression on me as a kid. Being literal, as kids are, the lesson seemed to be "give everything." Now I think of it in terms of spiritual wealth (or wealth of character, if you're not a spiritual person) versus material wealth.

I think the parable was intended to make us uncomfortable. It's saying, take stock of what you've got and "give of yourself." This will be different for every person. When it comes to money, it might not be a straight equation - a percentage or a line in one's budget.

I feel that I can and should sacrifice something in solidarity and support of the people of Japan. My monetary contribution, like the widow's, will be negligible in the grand scheme of the billions that are needed to piece their world back together. But if the parable holds true, it's still has value. All I'm giving up is the money I would have put into my vacation fund. Maybe that's not enough? I'll see how I feel. If it doesn't feel uncomfortable I will add more until it does.

I pray that the people of Japan will be able to sustain hope in such dark times. Hope is hardest when it is most needed.

I'm interested in hearing whether others have a set amount of funds for charitable giving, or how they determine what they will give. Thoughts?