Medical and Veterinary - Deer Tick
Fact Sheet (Univ. of Rhode Island): Deer Tick (also called Black-legged Tick — Latin name: Ixodes scapularis)
Engorged Deer Tick (LEFT) and Engorged Dog Tick (RIGHT) — note the difference in overall body size
See also the Maine Medical Center’s Ticks in Maine page for Lyme disease information, tips and photos. Also, the Maine Center for Disease Control & Prevention has a page entitled Ticks and Lyme Disease.
You can find a lot of additional images of ticks online at BugGuide.net