First of all, you'll want to visit these two sites:
http://www.erowid.org/ (Go to Plants & Drugs/Cannabis)
http://www.norml.org/ (Read the daily news and the Medicinal and Personal Use areas)

Then you should also visit our Medical area here and peruse the threads there. They're full of links to various health-related topics.
http://boards.cannabis.com/forumdisplay.php?f=10