New York Times provided a list of charities accepting donations to help the relief efforts in Beslan, Russia. These are:

Beslan Relief Fund of the Orthodox Church in America,
Consulate General of the Russian Federation
Embassy of the Russian Federation,
International Foundation for Terror Act Victims
Terror Relief Fund

I understand that 'Doctors Without border' has also sent a team of physicians to Russia. I personally think that governments or most large organizations have way too much unnecessary overheads that eat into the donations. I feel that Medicins Sans Frontieres is one of the exceptions. Almost 86% of what they spend every year go into program services (management overhead is about 2% and the rest go into fund raising)

They go to the worst places; They are usually among the first ones to go in and the last ones to come out. That is why their closure of programs in Afghanistan caused such shock waves.

Their donation page is here.