Macmillan Cancer Support
Cancerbackup: Chronic Lymphocytic Leukemia Information Center
This competent, comprehensive site defines leukemia in general and specifically looks at the causes, diagnosis, and treatment of chronic lymphocytic leukemia.
Other
Leukemia and Lymphoma Society: Leukemia
This excellent site lists the major types of leukemia and describes causes and risk factors, symptoms and signs, and other key information on this disease.