The Velveteen Rabbi has posted on the crisis in Sudan a number of times, and she's linked to Passion of the Present, which is full of information and resources. In her most recent post, she links to this Forward article, which discusses efforts by Jewish organizations to address the crisis. As I tend to be skeptical of human rights organizations, I was pleased to discover this appeal, by the American Jewish World Service. I haven't done any real research on AJWS, so I can't vouch for it, but they claim that "[a]ll emergency appeal funds (minus a five percent overhead) go directly to supporting relief efforts." Just as importantly, the appeals are compartmentalized, so you can choose to donate exclusively to the relief fund for the Sudanese.
The site also has a pre-written letter that can be sent electronically to George Bush, Colin Powell, and U.S. Ambassador to the United Nations John Negroponte, as well as to your senators and representative. As Lawrence has reminded me a number of times, paper letters are more effective than e-mail, so it's even better if you make a few copies of the message and drop them in a mailbox.
That's my two cents for the day. Shalom.