Center for Responsive Politics
Political junkies and anyone looking into a regulatory issue will appreciate the alerts from the Center for Responsive Politics, a nonprofit with searchable databases of U.S. campaign contributions. It's easy to look up campaign contributions here, with the usual limitation that there is a time lag between the contributions and reporting by the Federal Election Commission. Staff at CRP have the most useful publications and advice on covering campaign finance, and will provide data in a hurry, sliced the way you want, for a small fee.

DEBKAfile
Independent news source with focus on Middle East terrorism; has a distinctly hawkish, often pro-Israel bent (it was founded by 2 journalists in Israel) though it claims to have "no axe to grind." Provides news and tips about terrorism and intelligence from around the world that aren't necessarily reported widely.

FactCheck.org
A monitor of factual accuracy in US politics

Human Rights Campaign
Gay and Lesbian political news.

Taxpayers for Common Sense
An advocacy group opposing government waste, TCS publishes a "Weekly Bulletin on Wasteful Government Spending from Taxpayers." To subscribe, send an E-mail to majordomo@lists.his.com with no subject line and this as the only line of your message: "subscribe waste_basket@taxpayer.net youraddress." Fill in your E-mail address.

Women Leaders Online
AKA Women Organizing for Change. Publishes alerts on pending legislation affecting women.