Utilitarianism charityCharity International - dedicate themselves to specifically utilitarian goals, though the English language pages are a bit vague about what that actually means.
Charity evaluatorsGiveWell - the only active organisation that directly compares the effectiveness of charities' goals. [edited in after Toby's post, since it's such an important idea]
Giving What We Can - Toby Ord's had this almost ready to go for what feels like over a year, but once it's finally up I'm hoping it will be the first stop for someone who wants to know not just how efficiently their money is spent on a cause, but how efficient the causes are.
Links page to other evaluating organisations - for anyone who wants to do some serious research.
American Institute of Philanthropy - this page is a nice quick fix. It breaks down charities by activity and then shows you the 'top-rated' charities in your chosen category. Note that although they have a few criteria for their rating, all they're rating is how efficiently the charity promotes its cause. The value of its cause doesn't factor in (so, for eg, they have a category that includes both pro- and anti-gun control charities).
Ethical investmentTriodos Bank - as an alternative to giving your money to charity, you might invest it in an ethical savings account. Ethical accounts still seem to earn significantly less interest than nonspecific investment accounts, but they're by far the most committed bank to ethical investment that I know of (and you can weigh the loss of interest vs the amount you were planning to donate to charity and draw your own conclusions).
Established charitiesIn
Living High and Letting Die, the best argument I've read for charitable donation, Peter Unger specifically names two charities:
Oxfam and
Unicef - he also implies that, while they have several operations, both charities are organised enough that you can ask when you donate that your money goes to the area where it will do the most good.
I'd like to see something about environment/population control/animal welfare charities, but I don't know anything about them that 30 seconds on Google or the above links wouldn't reveal...