The state flag of Maine was adopted in 1909. It displays Maine's coat-of-arms on a field of blue (the same shade of blue as the USA's star spangled banner). Above the coat of arms shines the North star* and Maine's motto: "Dirigo" (I Lead, or I Direct), below is the word MAINE in capital letters.

Maine's official state seal also displays the state's coat of arms. The farmer is a symbol of pride in Maine's agricultural roots. The sailor represents Maine's strong ties to the sea. Symbols of the natural richness of the state are pictured on the center shield - a pine tree, a moose (Maine's official state animal), sea, and sky.

*The North star (Polaris) also appears on the state flag of Alaska. Polaris is not merely a symbol of guidance - travellers have depended on it for many centuries to find their way (it always marks due north).

Source:

Maine State Symbols - State Flag: Maine SOS Kid's Page
The Great Seal of the State of Maine: Maine SOS
The Story of Maine: Institute of Mueum & Library Services
Maine state symbols - flags of Maine: Dave M's Flag Pages

Links:

Maine Facts & History: Official Website State of Maine
All About Maine History: Maine SOS Kid's Page
All State Flags - National Flag