Introduction to Climate Change
This page isn't up and running yet, In the meantime you could try the pages of the IPCC, the international scientific panel on Climate change. The summary for policymakers of the 3 working groups which produced the 1995 Scientific Assessment report gives a general background to some of the likely effects of climate change.
For information on climate feedbacks, which are by and large left out of the IPCC reports, yet could lead to catastrophic scenarios, read Ben Matthew's review of them.
And if you just want to be reassured that everything is OK and we can go on polluting as much as we like, then try the industry sponsored Global Climate Coalition, but be warned, the opinions expressed on this site are heavily influenced by money!
New Scientist Magazine has a good general introduction to the science and effects of climate change.
