The obvious ones:
Spencer - ENTJ, she's the walking definition of this type. Her need for people to acknowledge her intelligence is indicative of a dominant Te and her precise plan for her future (before this season of course) indicates a strong Ni. People mistake her for an introvert because she's studious, but she enjoys being around others all the time way too much for that to be the case.
Aria - ISFP, I'm surprised no one's noticed this. She's literally the definition of this type. Though she's opened up a lot throughout the series, she's clearly an introvert. She screams dominant Fi because she's not about making the rational decision, she's all about following this inner moral code that she's established. Her secondary Se also shows in how fashion forward she is and her willingness to forgive all of the shitty things that Ezra does (an Si would not overlook the things Ezra has done so easily).
The obvious once you really look:
Hanna - ESFP, I originally had Hanna pegged as an introvert because of how quiet she was in flashbacks, but it became apparent to me that wasn't her natural state. Her dominant Se shows in her strong fashion sense and her awareness of everything going on around her (if you pay attention Hanna is usually the one to point out something strange happening around them). Her secondary Fi becomes obvious the second her moral code is violated. She will often neglect the rational solution to go for the one that suits her personal feelings more.
Allison - ENFJ, this type is known for being super sweet, but Allison is an ENFJ gone wrong. She uses her dominant Fe to read the emotions and motivations of those around her and manipulate them to her desires. Her secondary Ni shows in how she intuitively knows things about her friends without being told and her clear vision of her future. It took me a while to come to this type, but once I did I was like "Duh! It was staring me in the face!"
Toby - ISFJ, his dominant Si is extremely apparent in the first two seasons of the show. He detaches himself from the world and lives in the past (specifically the bad moments like The Jenna Thing and Allison's torment). His secondary Fe can easily be missed, but it's apparent because of how much Toby cares about others' feelings and specifically what they think about him (such as the moment when Toby was walking down the street and everyone ran away from him, pre-exoneration obviously, so he ran into an alley to cry).
Caleb - ISTJ, so obvious and I'm angry at myself for almost missing it. His dominant Si is so apparent. Anybody remember when he got back from Ravenswood? His body was in Rosewood, but his mind was not. He clearly prefers logic over emotions also, but when he gets in an emotional state he usually becomes unreasonable and will always stick firmly to his moral code/personal emotions (leading me to see Te-Fi). His friendship with Toby works because they're so similar.
The not so obvious:
Emily - ISFJ, it was between this and INFP, but I decided on ISFJ because she does not have the traits of a dominant Fi at all. Her dominant Si is apparent in the way she is constantly reliving past memories (like her times with Allison). Her secondary Fe shows in the way that she often becomes the peacemaker among her friends. She also refrains from coming out initially because she's afraid of what people will think of her (something an Fi dominant would never do). She and Toby must have connected and understood each other so quickly because they have the same type.
Mona - ESTJ, I'm confident about this typing, but she could be something else. Mona's definitely an extraverted thinker, as she has no trouble chatting people up and showing off her logical prowess. Her secondary function as Si also makes complete sense as the girl totally lives in the past (I mean she became A because of Allison's torment for goodness' sake).
Ezra - INFP, Ezra strikes me as the person in the group that lives the least in reality. He's obviously an introvert (despite how well he copes with social situations during the day) as he immediately retires to his apartment or some other solitary activity when he's off the job. Ezra clearly is feeling dominant as he rarely makes decisions rationally and opts to make his decisions based on his moral code. I chose Ne-Si because Ezra seems to not really acknowledge reality often. In the early seasons Aria had to be the one to bring him back to reality. I'm actually finding it hard to think of concrete examples because of how much Ezra is in his own world most of the time. This also might be why so many find him to be boring. Since he lives in his own world, he often distracts from the things actually going on in the town.
I don't really care enough about any other characters to type them. I'm pretty confident in my decisions on these character's types.