Good general information on lots of dermatology topics:
American Association of Dermatology www.aad.org
Skincare Physicians www.skincarephysicians.com
Dermatology Surgery Society www.asds-net.org
Information on specific disorders; many of these sites include both medical information and support groups:
Acne www.skincarephysicians.com/acnenet
Actinic keratoses www.skincarephysicians.com/actinickeratosesnet
Aging skin www.skincarephysicians.com/agingskinnet
Alopecia www.alopeciaareata.com
Congenital nevi www.nevus.org (moles present at birth)
Cutaneous T-cell lymphoma, including mycosis fungoides www.mffoundation.org
Dermatitis Herpetiformis www.gluten.net (information on gluten-free diets)
Eczema www.nationaleczema.org www.skincarephysicians.com/eczemanet
Lupus www.lupus.org (systemic lupus erythematosis)
Melanoma www.melanoma.com www.skincarephysicians.com/melanomanet
Pemphigus www.pemphigus.org (a chronic blistering disease )
Porphyria www.porphyriafoundation.com (a group of genetic disorders)
Psoriasis www.psoriasis.org www.skincarephysicians.com/psoriasisnet
www.nlm.nih.gov/medlineplus/psoriasis.html
Rosacea www.rosacea.org www.internationalrosaceafoundation.org
ns.com/rosaceanet www.skincarephysicians.com/rosaceanet
Skin Cancer www.skincancer.org
Tuberous Sclerosis Complex www.tsalliance.org
Vitiligo www.nvfi.org