A typologically well-balanced show, if I may say so. (Could use another N.)
I always thought it was kind of perfect the way the core family unit on this show worked because of what I'd call the "two degrees of separation" (although these vary widely from some of the preceding opinions):
Seth -- INFP, tending towards ENTP. Comic genius, obvious Ne, but lazy and extremely self-possessed.
Ryan -- ISTP -- passionate about building/design, chivalrous Fe intentions get out of control.
Kirsten -- (i)SFJ -- Bears responsibility for everything! "I'm never throwing another party again."
Sandy -- ENF(j) -- "^Oh honey, don't tease."
One of my favourite bits of dialogue from the show.
Marissa -- (i)SFP -- Most likely to say: "Leave me alone."
Summer -- ESFJ -- Most likely to respond with: "But you'll feel better if..."
Taylor -- ESFJ -- Essentially Summer, but alienated from nurturing figure with interesting social consequences.
Julie -- ESTP -- Needs to appear in control, overprotective to atone for own early adulthood mistakes. Strong image-focus represents direction of unconscious pull for most of the greater community.
Jimmy -- (e)SF(p) -- Bonded closely to Marissa by shared values, but not a well-developed character.
Caleb -- ISTJ -- Personifies the corporate establishment, but pathologically private.