Here's a list of links you may find useful:

Environmental

Action Network -Environmental Defense. Become an E-Activist! Save the Environment with the Click of Your Mouse!
Care 2 Environment Supersite -Free email and e-cards that help to save animals and endangered species, healthy tips, eco news and petitions to sign.
Co-op America -Practical steps for using your consumer and investor power for social change. They offer Green Pages Online (10,000 green products and businesses), Boycot Action News, personal finance and investing info for green-conscious folks, and much more!
Environmental Defense Fund -This leading national non-profit organization has more than 300,000 members and has been around since 1967. They have linked science, economics, and law to create innovative, equitable, and cost-effective solutions to the most urgent environmental problems.
Green Money Journal -Responsibility from the Supermarket to the Stockmarket.
Greenpeace -Gather information, interact with them and join them in theirstruggle to keep the world safe from ourselves! Focus on climate, toxics, nuclear, oceans, genetic engineering, ocean dumping and forests.
Mother Jones -Celebrating 25 years of raising hell. They have web exclusives that aren't found in their monthly magazine.
Institute For Global Communication -Connecting People Who are Changing the World. They have links to PeaceNet, EcoNet, WomensNet and Anti-RacisimNet.

Women's Issues

The Breast Cancer Site -Also connected to sites devoted to: world hunger; childeren's health; literacy; animal rescue and the rainforests. A great way to connect with charitible organizations associated with each cause
The Feminist Majority -This site empowers women through research, the sharing of information and effective action. Fax your Member of Congress from their site, check out their events calendar or donate to the cause, plus lots more.
N.A.R.A.L. -The National Abortion and Reproductive Rights Action League. Up-to-date information and ways to make a difference on choice issues.
National Organization for Women -They've got Action Alerts, News Highlights (including their "Outrage of the Week"), an Activist Toolkit (Write to Congress, Tell the Media, Send an e-Card, Sign a Petition) and many interesting articles that you just won't see anywhere else!

GLBT

365Gay.com -Get the daily Gay & Lesbian Magazine online!
Gay & Lesbian Alliance Against Defamation -GLAAD is dedicated to promoting and ensuring fair, accurate, and inclusive representation of individuals and events in all media as a means of eliminating homophobia and discrimination based on gender indentity and sexual orientation.
Parents, Families & Friends of Lesbians &Gays -PFLAG is a national non-profit organization with over 80,000 members and supporters and more than 460 affiliates in the U.S.A. They celebrate diversity and envision a society that embraces everyone, including those of diverse sexual orientations and gender identities.
Pam's House Blend -A gay and lesbian blog, but a wide range of current issues are brought up here.
Quatrefoil Library -A collection of GLBT materials focusing on diversity and history, and the value of communities.

Indigenous Rights

Resource Center of the Americas.org -This grassroots site is dedicated to news, analysis and campaigns on Latin America and globalization.
AIM Movement.org -Grand Governing Council -This is THE main site for the AIM movement. You can read about how AIM formally started 1968 out of the violence of police brutality in Minneapolis, MN and the voiceless despair of Indian people in the courts. AIM is attempting to connect the realities of the past with the promise of tomorrow. They are the Warriors Class of this century, who are bound to the bond of the Drum, who vote with their bodies instead of their mouths. Their business is hope.
Leonard Peltier & AIM Information--From -The People's Path Background, articles, links, news, updates, and much more!
Leonard Peltier Defense Committee -The LPDC seeks the immediate release of Leonard Peltier. The LPDC is the center of communication between Leonard Peltier, his supporters, his family, the media, key government officials, and all other relevant persons.
Western Shoshone Defense Project -Their mission is to affirm Newe (Western Shoshone) jurisdiction over Newe Sogobia (Western Shoshone homelands) by protecting, preserving, and restoring Newe rights and lands for present and future generations based on cultural and spiritual traditions.

Politics

Air America Online -You can Listen To Air America radio online from this site, as well as accessing some expanded content on current issues.
Crooks and Liars -Up to date news, with quite a few video streams, generally dealing with politics but not always.
MAPLight Campaign contributions and how legislators vote. Connection between money and politics.
The Nation -Offering unconvetional wisdom since 1865. If you don't know about the Nation, check it out and see what you've been missing.
The Center For Public Integrity -Their mission is to provide the American public with the findings of its investigations and analyses of public service, government accountability, and ethics-related issues via books, reports and newsletters.
Democrats.com -They're the largest independent community of democrats. They're the "aggressive progressives!" Join 'em, get their newsletter, and be progressive!
East Timor Action Network/US -ETAN/US is a member of the International Federation for East Timor, they support La'o Hamutuk (Institute for Reconstruction Monitoring & Analysis, and they work with the Indonesia Human Rights Network.
Health Care Without Harm -Their mission is to transform the health care industry worldwide, without compromising patient safety or care, so that it is ecologically sustainable and no longer a source of harm to public health and the environment.
Jews for Justice for Palestinians- Both Israel and Palestine have a right to exist.
March On the RNC-The Republican National Convention in Minneapolis / St Paul.
Michael Moore -You can read his Oscar speech here on his site, sign up for his newsletter, and be assured he'll tell you non-fiction, as opposed to the stories and lies we're all used to hearing. Order "Bowling for Columbine" from his site and support his work.
Peace & Justice Center, Burlington, VT -Since its inception in 1979, the Peace & Justice Center has been involved in projects that address the fundamental causes of Vermont's social, economic, and racial problems, as well as national and international areas of concern, through campaigns, educational programs, and anti-racism training that promote racial justice, equity, economic justice, democracy and civic participation.
Progressive Action Alliance -Promotes progressive candidates, ideas, and issues through action, advocacy, education,and networking.
People for the American Way -These folks are committed to defending democracy and bringing the ideals of community, opportunity, diversity, equality and fairness together to form a strong, united voice. They conduct research, legal and educational work, and monitor and research the Religious Right movement and it's political allies.
Protest.Net -These folks offer a calendar of protests, meetings and conferences. Check for protests in your region, read the protest news, or post an upcoming protest in your area.
Support Sanity.org -These folks are building massively-visible support for an even-handed, two-state solution for Israel and Palestine. Buy their pin and support their cause!
Teaching For Change.org -They provide curriculum guides and other resources to help teachers engage students in innovative classroom activities that deal with issues of equity and social justice. They have an online catalog of hundreds of multicultural anti-racist books, videos, posters, and other classroom resources.
True Majority -Founded by Ben Cohen from Ben & Jerry's Ice Cream, True Majority is a grassroots education and advocacy project of Priorities, Inc. Register with them and you can send faxes to your congresspeople and national leaders.
The World Socialist Party -This site is a collaborative work of socialists around the world.

Vegetarian

Veggie123.com -How to become a vegetarian.