One of the obligations of Purim is Matanot La’ebyonim, which requires giving to two different needy people at least enough money for a meal, which amounts to approximately $5-$10 to each of the two poor individuals. Many people donate money to a fund before Purim that distributes the money it collects among underprivileged people on Purim, and this is a perfectly acceptable method of fulfilling the Misva.
Hacham Ovadia Yosef rules that one may even give money before Purim to a fund that will distribute the money to poor residents of Jerusalem on the 15th of Adar, when Purim is celebrated in Jerusalem. Although outside Jerusalem we celebrate Purim on the 14th, nevertheless, one fulfills the obligation by giving charity that will be given to poor people in Jerusalem on the 15th. As long as the money will be given to people in need on the day they observe as Purim, the Misva is fulfilled. Moreover, Hacham Ovadia adds (listen to audio recording for precise citation) that by supporting the needy residents of the holy city of Jerusalem one fulfills the Misva at an especially high standard, and earns special merit.
(Based on Yalkut Yosef – Purim, p. 185)