Proper Resonance Structures
Yes, they are all valid resonance structures.  In the first series, there is a third resonance structure you could draw with the negative charge alpha to the carbonyl carbon. In the second series, the phenoxide anion, you can draw two more structures.  One with the negative charge in the other ortho position and one with the negative charge in the para position.  This significant resonance stabilization of the phenoxide anion explains why phenol is such a strong acid.  In your third series there is also a third structure with the positive charge situated alpha to the nitrogen.