I think the human suffering alone is sufficient reason for contributing to the relief efforts in Pakistan, but Robert Reich makes another case:

If you’re not moved by the scale of the disaster and its aftermath, consider that our future security is inextricably bound up with the future for Pakistan. Of 175 million Pakistanis, some 100 million are under age 25. In the years ahead they’ll either opt for gainful employment or, in its absence, may choose Islamic extremism.

We are already in a war for their hearts and minds, as well as those of young people throughout the Muslim world.

Right now, Islamic insurgents are using the chaos as an opportunity, attacking police posts in Pakistan’s northwest while police have been occupied in rescue and relief work. Meanwhile, lacking help and losing hope, many Pakistanis are becoming increasingly hostile toward President Asif Ali Zardari.

In addition to straight cash aid, Reich highlights other things the US could do:

While they’re at it, Congress should remove all tariffs on textiles and clothing from Pakistan. Textiles and clothing are half Pakistan’s exports. More than half of all Pakistanis are employed growing cotton, weaving it into cloth, or cutting and sewing it into clothing. In the months and years ahead, Pakistan will have to rely ever more on these exports.

Yet we impose a 17 percent tariff on textiles and clothing from Pakistan. If we removed it, Pakistan’s exports would surge $5 billion annually. That would boost the wages of millions there.

That tariff also artificially raises the price of the clothing and textiles you and I buy. How many American jobs do we protect by this absurdity? Almost none. Instead, we’ve been importing more textiles and clothing from China and other East Asian nations. China subsidizes its exports with an artificially low currency.

Cash aid is an important and essential part of disaster relief, but this tariff reduction is the sort of long term aid that can really make a difference.  I’d add lots of caveats and exceptions to it, but it’s a step in the right direction.