Which atoms are sp^2 hybridized (with diagram)

                H                             H        H         H     H
..      ..      |                               |         |           |      |
O===N-----C-----C(3 bonds)C------C-------C==C==C----C----H
``              |                               |                           |
                N:                           :O:                         H
                /\                              |
              H  H                           H

I'm a little lost, so any help would be appreciated.

Any atom with a double bond and two single bonds (like two of the C atoms on the right) or a double bond, a single bond and a lone pair (like the N on the left) are sp2 hybridised.

The double-bonded carbons, certainly. Not sure about the O=N, I have a nagging doubt about them, something about nitrogen not permitting hybridisation.

Sorry, it's been a long time since I did organic. I teach physical and inorganic now.

H H H H H
.. .. | | | | |
O===N-----C-----C(3 bonds)C------C-------C*==C==C*----C----H
`` | | |
N*: :O: H
/\ |
H H H

The atoms which i have placed a '*' (star) next to are sp2 hybridised. That is. The one Nitrogen and the 2 carbons.