The Intergovernmental Panel on Climate Change (IPCC) is the best, and most thorough source of information about the issue. The panel was formed by the UN in 1988 and they have just released the first three sections of a four part report that has been in the making for the past 6 years. Over that time they have enlisted the work of 2500+ scientific expert reviewers, 800+ contributing authors, and 450+ lead authors from 130 countries to put together a comprehensive analysis of the causes, impacts, and solutions to global climate change.
Listed below are links to the "Summary for Policymakers" sections of those three reports. On November 17 they will release a fourth report that pulls all of these together.
Working Group I - The Physical Science Basis (18 pages) - http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf
Working Group II - Impacts & Vulnerability (16 pages) - http://www.ipcc.ch/SPM13apr07.pdf
Working Group III - Mitigation of Climate Change (24 pages) - http://www.ipcc.ch/SPM040507.pdf
By the way, the IPCC (who actually did the scientific work to quantify the problem and the potential solutions) are co-recipients of the Nobel Peace Prize with Al Gore (who has publicized their findings).
The general consensus among the scientific community is that the planet is warming, that carbon dioxide and other greenhouse gases are the cause, that human activity is the source of most of those gases, and that continuing the trend will have significant negative consequences. While some warming is already happening and will continue to happen based on emissions that have already occured, we can minimize the impacts of global warming by dramatically reducing our carbon output. The best estimates are that if we reduce the amount of greenhouse gasses emitted by 20 percent by 2020 and by 80 percent by 2050 then we could avoid the catastrophic impacts of climate change.
Environment Maryland, a local non-profit group, came out with a report this summer detailing the ways in which emissions in Maryland could be cut to meet those goals. They involve some costs and sacrifices, but longer term benefits and most of these would save money in the long-range and reduce our dependence on oil from the Middle East (another benefit, especially as costs increase and the supply diminishes). Environment Maryland, the Sierra Club, and other local groups are working to encourage Governor O'Malley to commit to the 20/20 and 80/50 goals as part of his agenda.
The NewsHour with Jim Lehrer also has a good site focused on the Climate Change debate with information from all sides of the discussion. http://www.pbs.org/newshour/indepth_coverage/science/globalwarming/index.html
The Weather Channel also has an extensive set of articles and data. http://climate.weather.com/
NASA's Goddard Space Flight Center has some more information and links if you need more information. http://globalchange.nasa.gov/Resources/pointers/glob_warm.html
Here are two timelines on the history of climate change activities and research.
A couple of scientists at the University of Arizona have set up a site where you can see what the impacts of different amounts of sea level rise would be, from minimal up to 20 feet. Sea level rise is one expected impact of climate change but with limited clarity about the amount and timing of potential changes. http://geongrid.geo.arizona.edu/arcims/website/slrus48prvi/viewer.htm
The City of Baltimore and other local jurisdictions have begun making commitments to make changes to reduce their climate impacts, and some have started making policy changes based on that commitment. A list of some of those jurisdictions can be found at: http://coolcities.us/state.php?state=MD or http://www.kingcounty.gov/exec/coolcounties
AND, for a totally different take on global warming, here's what Sarah Silverman has to say. http://sarahsilvermanonline.com/globalwarming.html