A lot of people are reposting appeals for Kony 2012/Invisible Children. Before you give money or repost, I urge you to read the following:
"Think Twice Before Donating to Kony 2012, the Charitable Meme du Jour" at Jezebel and
Visible Children Visible Children warns not only that this "charity" spends the vast bulk of its money, but it supports military interventions by armies with histories of war crimes.
The Charity Navigator page for Invisible Children is worth seeing--particularly at the bottom, where it is compared with other charities with similar missions, and in the middle, where the financial data are given (including administrative expenses of over 16%; Doctors without Borders, by contrast, is under 2% there).
Invisible Children responds here, so you can read their answers too before you decide.