I'm not really a political animal, though I'd like to get involved more. Check out my comments on "loyalty".

For:
1. Gay and lesbian rights
2. Removing religion
Women's rights
Equal rights for minorities
Public education
Social welfare
Abortion choice
Free speech
Feminism
Single-payer healthcare
Immigration
"Right-to-die" laws
GMOs and genetic engineering
Paying down the deficit
Cheap housing for the poor
Teaching evolution in schools (and science in general)
Giving more power to the USDA to regulate slaughterhouses
Transgender issues
Legalizing marijuana
Prison system reform

Against:
School vouchers
The "poverty industry" (check cashing, rent-to-own, cheap credit schemes, etc.)
Insurance companies
Pseudo-science
Alternative medicine
Military spending
The flat tax
"State's rights"
Mother Theresa
Religion

Ambivalent:
Guns
The free market and other libertarian issues
Animal rights
Vegetarianism
Social security
The death penalty
"English only" education
Legalizing other drugs besides marijuana
Crime
Global Warming

Here are some liberal resources and links:

Alliance for Democracy
http://afd.online.org

Campaign for America's Future
http://www.ourfuture.org

Center on Budget and Policy Priorities
http://www.cbpp.org

Center for Community Change
http://www.communitychange.org

Center for Public Integrity
http://www.publicintegrity.org

Center for Responsive Politics
http://www.opensecrets.org

Center for Study of Responsive Law
http://www.essential.org

Citizens for Tax Justice
http://www.ctj.org

Common Cause
http://www.commoncause.org

Economic Policy Institute
http://www.epinet.org

Environmental Defense
http://www.environmentaldefense.org

Fairness and Accuracy in Reporting (FAIR)
http://www.fair.org

Farm Aid
http://www.farmaid.org

Financial Markets Center
http://www.fmcenter.org

Global Exchange
http://www.globalexchange.org

Global Trade Watch
http://www.citizen.org

Independent Media Institute
http://www.alternet.org

Institute for Agriculture and Trade Policy
http://www.iatp.org

Institute of Policy Studies
http://www.ips-dc.org

The International Law Project for Human, Ecological, and Environmental Defense (HEED)
http://www.heed.net

Jobs With Justice
http://www.jwj.org

National Farmer's Union
http://www.nfu.org

National Labor Committee
http://www.nlcnet.org

National Low Income Housing
http://www.nlihc.org

National Priorities Project
http://www.natprior.org

New England Burma Roundtable Trillium Asset Management
http://www.trilliuminvest.com

The Preamble Center for Public Policy
http://www.preamble.org

The Program On Corporations, Law, and Democracy (POCLAD)
http://www.poclad.org

Public Campaign
http://www.publiccampaign.org

Public Citizen
http://www.citizen.org

Rocky Mountain Media Watch
http://www.bigmedia.org

Sustainable Energy and Economic Development (SEED) Coalition
http://www.seedcoalition.org

TomPaine.com
http://www.tompaine.com

United for a Fair Economy
http://www.stw.org

United Students Against Sweatshops
http://www.usanet.org

US Public Interest Research Group (PIRG)
http://www.pirg.org