Maine's new Constitutional Carry, or Permitless Carry, law becomes effective on October 15, 2015. On that date, anyone who 21 years of age or older (or 18 years of age and on active duty in, or honorably discharged from, the US Armed Forces the National Guard) and not otherwise prohibited from carrying a firearm may carry a concealed handgun without obtaining a permit from the government.
The text of the new law can be read at http://www.mainelegislature.org/legis/bills/getPDF.asp?paper=SP0245&item=19&snum=127 .