Good thread, sarbuze.
Like Aresenal4ever, I used to give to big, well-known charities but became jaded after realizing most of each dollar raised went into administration, marketing, mailers, staffing etc.
Charity Intelligence researches Canadian charities on their transparency, accountability, need for funding and operational efficiency, assigning each a rating from one to four stars. It's a great way way to decide where your charitable dollars will be best used. A quote from Warren Buffett on their home page says it well: "Giving money away is easy. Giving money away well is fiendishly difficult." I don't know if there's a comparable site for US charities.
Much of my charitable giving goes to one of those four-star charities,
Sleeping Children Around the World, which provides bed kits, mosquito netting and other supplies to children in impoverished countries. Virtually every penny contributed goes towards the kits, and the entire charity has exactly one staff member. Volunteers do everything else, including paying their own travel expenses to distribute the kits where needed. That's my idea of a worthy charity.