Random over-generosity is not a particularly effective charity pattern. If you feel that Hacker News denizens like ourselves happen to have too much money, there are a variety of organizations which can transmit sums of money to those in need: not just a one-time $15 at random with a special tax diverted to prop up the Cuban government, but on a recurring basis, every month, as part of a program to help eliminate worldwide poverty in a targeted manner, and sensitive to the dislocations that can come about as a result of carelessly deployed aid.
I use WorldVision to do this, personally (some of their non-evangelizing programs) as I appreciate their efficient organization, but there are other ones out there too. I can supply links to https://www.worldvision.org/donate and suggest interested parties consider a $40/mo sponsorship of a child's health and education at https://www.worldvision.org/sponsor-a-child