Just to be clear, this isn't a *hiker* hostel, but I thought I'd share here anyway. I just saw the other day that some folks are opening a travelers hostel in downtown Portland. Not really any info on it just yet, except that it's located within walking distance (for normal people, not just hikers) of most of the good stuff in town, and they say it'll be open in June this year.
Probably not of too much interest for AT folks, except as potentially affordable lodging in the city while you're on your way into or out of Maine.
https://www.facebook.com/pg/blackelephanthostel/about