eMedicine: Actinic Keratosis 
Describes the risk factors, appearance, pathology, treatments, and possible outcomes. Includes photographs of treated and untreated lesions.
http://emedicine.com/derm/topic9.htmSun Damage
Explains how pre-cancerous lesions develop, their risk factors and treatment, and includes photographs of these and similar conditions.
http://www.dermatology.co.uk/sun/sundamage/
Solar Keratosis
Patient fact sheet explains causes, appearance, diagnosis, risks, and treatment.
http://www.patient.co.uk/showdoc/27000241/
Solar Keratosis
An outline of the condition and the need for treatment, with a link to a series of photographs.
http://www.skinpatient.com/ptinfo/S/solarkeratosis.htm
Healthopedia.com: Actinic Keratosis
A detailed explanation covering symptoms, diagnosis, management, and outcomes. Includes discussion of the possible side effects of treatment, as well as the consequences of leaving them untreated.
http://www.healthopedia.com/actinic-keratosis/
