http://www.ncbi.nlm.nih.gov/pubmed
One of the best search engine for medical articles.

http://www.auanet.org/content/homepage/homepage.cfm
Official website of the American Association Of Urology.

http://www.who.int/en
Official website of the World Health Organization.

http://www.cancer.gov
Offiacial website of the National Cancer Institute.

http://www.uroweb.org
Official website of the European Association of Urology.

http://www.eortc.be
Official website of the European Organization for Research and Treatmen of Cancer.

http://www.cancer.org/docroot/home/index.asp
Official website of the American Cancer Society.

http://www.cochrane.org
Global network for collecting and reviewing medical data, based upon medical evidency.