American Society for Therapeutic Radiology and Oncology (ASTRO) provides excellent information for cancer patients and the general public as well as for its members and other physicians and healthcare professionals.
The National Cancer Institute (NCI) has a publication called "Therapy and You: A Guide to Self Help During Treatment".
Siemens Oncology provides information on radiation therapy.
Additional cancer Web sites and cancer resources are listed in the section on Cancer Prevention, Diagnosis and Treatment under More Information on Cancer.