If I cast a touch spell, such as Bull Strength, does it provoke an Attack of Opportunity? I realize that touch attack spells do not, but is that still the case if I'm not attacking?
As per PRD combat chapter, casting a spell provokes an attack of opportunity. There is no exception for touch range spells.
As for the touch attacks with a spell, it is the act of attacking itself which doesn't provoke an AoO; the act of casting still does.