Frontotemporal Dementias
The Association for Frontotemporal Dementias

Lewy Body Dementia
Lewy Body Dementia Assoc.

Vascular Dementia
Alzheimer's Association

Other specific diagonoses:
Huntington's Disease:  Huntington's Disease Society of America
ALS (Amyotrophic Lateral Sclerosis) or Lou Gerhig's Disease:  ALS Association
Atypical Parkinson's
Multiple Sclerosis
CADASIL:  The CADASIL Trust