I focus my efforts locally, where I have a better idea of the impact that they have. To be more specific, a nun at my church runs a "Needy Family Fund". Sister Paulanne is like a young Mother Theresa attending to the needs of local families who have experienced financial difficulties, loss of breadwinner, serious illness etc.
I feel better knowing where my money is going, rather than the "mass marketing" charitable groups who bombard you with TV ads, and bulk mailings. To be fair to some of these groups, however, I should point out that I inquired about the Feed the Children organization. I asked for there federal tax report, which includes overhead and administrative expenses, etc. I was pleased to learn that they do have a pretty low ratio of overhead expenses. I do contribute some to them as well.
I applaud you on your concern for giving back. I began my focus on charitable efforts a few years ago, when I was struck with the guilt over my interest (and investment) in my car. I realized just how selfish I was when I devoted all kinds of time, effort and money into a car that was just being used as a toy, and there where people in the world that were starving. I became so troubled by this, in fact, that I sold my car (a 95 993) and gave 50% of it the proceeds to charity. I also set up a weekly payroll deduction to direct deposit into my "Charity Account", so that I would be giving a little each week (which made it easier to budget). When I accumulate a fair amount in the account, I write a check to one of the charities that I support.
I have to admit, I still struggle with the balance (and justification) for my interest in Porsches, but, I feel much better that I am now giving back. After several years without a Porsche, I purchased one this past summer. My outlook now is that if I can buy a car at the right price, and make prudent decisions with respect to any improvements, I should be able to enjoy the car at very little risk of depreciation. While very few cars are ever able to be justified as an investment, owning a classic Porsche that holds it's value is not something I see as a irresponsible use of money.
Good luck.
edit: Sorry for "spilling my guts,"....I missed my therapy session this week.
