I just sent out an e-mail update asking people to write to the U.S. Ambassador to Pakistan. Below is a sample letter. Be sure to write "attn: Ambassador Patterson" as the subject.
The e-mail address for the U.S. embassy in Pakistan is email@example.com
Dear Ambassador Patterson,
It has been brought to my attention by several of my Christian friends in Pakistan that Pakistani Muslims have been attacking Christian villages and burning down their homes and churches, all because of trumped up charges due to the "blasphemy law." I am particularly appalled by what took place in the town of Gojra last week, where over 50 homes were burned down and 9 people were killed. My Pakistani Christian friends have told me that this is the third incident in Punjab this year. They also tell me that the rioting of the radicals is still going on and that the Pakistani police and military is not doing enough to protect them.
I believe it is the job of governments to protect their citizens, not to turn a blind eye to such gross human rights abuses. I am writing to ask you to apply the full use of your diplomatic resources to pressure the Pakistani government to repeal the blasphemy law, arrest the rioters and bring them to justice, and to provide immediate humanitarian relief and protection to the Christian minority in Punjab.
Thank you for giving your attention to this matter.