This is a basic overview of the science behind global warming. It briefly discusses the some of the controversy around the issue.

This is an article about the evolution of the american evironmental movement. It specifically addresses the tactics that environmental group use to accomplish their goals.

An absolutely huge list of links to various specialized search engines, statistic and trend collecting sites, and free resources for research. It's kind of a Swiss army knife of links with plenty of corkscrews that you'll never use but occasionally that fish scaler comes in handy in a bind.

Wikipedia can be a good starting place for research. As a collection of user knowledge it can sometimes be woefully inadequate but often  the references in the footnotes can lead to more academic sources on a topic.

A modified Google search engine that just searches within academic resources. This way one can avoid pulling up links to non-scholastic sources (like online discussions bereft of supporting data).

This page from Cornell University Library gives a step by step break down on how to find a good research topic. The steps on testing the strength of your topic seems particularly helpful at this beginning stage of the research process.

This page describes some suggestions on how to choose a research topic for a school assignment. It could be helpful at the start to avoid some pitfalls and get a good start on the research paper.