CancerBACUP: This site, from the United Kingdom, is staffed by oncology nurses.
British Columbia Cancer Agency: This Canadian site and has numerous nursing resources including drug information and protocols.
www.breastcancer.org: Provides information on all aspects of breast cancer, has a section of pictures of various breast cancer procedures and terms.
www.susanlovemd.org: Dr. Love's site touches on many aspects of breast cancer. I have found her "frequently asked questions" section particularly useful.