I'm joining the army and I want to be a psychologist when I get out. What jobs deal with psychology?

There aren't really any that are going to deal directly with that unless you were a psychiatrist and came in that way.  I would try to go in as a corpsman and talk to a detailer about being put into a psychiatric billet.  They will not be able to guarantee it since you will probably just get stationed to the hospital but I am not certain about that.  But I would say corpsman would be the way to go if that is what you are interested in.  Good luck.

The navy has Corpsmen who have an NEC to work as Psych Technicians at navy clinics and hospitals.

I used to be what they called a Behavioral Science Specialist and the MOS was 91Golf. This was in the early 1990's...but I think the Army calls it something different. You'll be working in the Mental Health Clinics doing intake screenings, counseling, Psych testing for the Psychologists (such as MMPI, WAIS IQ testing and things of this nature. You might also be doing some Chemical Dependency Counseling)
If you have a college education in Social Work, Psychology, etc...try to get into OCS to become an officer first. They also have two other psychological MOS's but I forget what they are called.

Ask the recruiter for specific details. Your schooling will be at Ft. Sam Houston Academy of Health Sciences located in San Antonio, TX. Excellent school and traing which lasts about 6 months total.