I know that the following hospitals do have new grad positions (though I haven't seen any recently
Eastern Maine Medical Center ( I applied for this back in the day, you are NOT eligible if you have already passed NCLEX)
Maine Medical Center has Clinical Nurse I positions, though I rarely see them open
Parkview Adventist Medical Center - They don't have one, its just 3 units, med/surg, ICU and ER. Its a good place to learn but no formal program
Also Mercy Hospital is the other hospital in Portland, and St. Mary's is the other in Lewiston, worth looking into but no idea of what they do for new grads.
Central Maine Medical Center - They had new grad positions in the past, I don't know about this year.
Those are the big ones. Good luck!