Is it permissible to give zakat al-mal to organizations concerned with helping Muslims affected by the Sumatra earthquake in Indonesia, and is it permissible to pay two years' worth of zakat in advance for such circumstances?

If institutions will disburse Zakat (definition) to its legitimate recipients, then it is permissible to pay Zakat to them and authorize them to deliver it to those who are eligible. It is permissible to pay Zakat in advance for a year once the nisab (definition) is reached, especially if there is a benefit in doing so, although it is preferable not to. This is because some scholars stipulate that the Zakat recipient must still be eligible when the next hawl (full lunar year) passes, and it may be difficult for the Zakat payer to ascertain this.