When Bob Maplethorpe and Dignan come back to the motel room to find a party in progress, one of the maids who is sitting on the bed with Rocky and Inez is wearing a party hat that disappears and reappears between shots without her taking it off.
The room Dignan and the boys stay in is a non-smoking room, there is a big white sign on the door. After Dignan is beaten up and they're back in the room, Inez leaves and you see the sign on the door. Anthony leaves a second later, and the sign is gone.
After the bookstore robbery, while at the house after the robbery while celebrating and talking back and forth, you can clearly see police lights flashing behind the trees, which are behind Owen Wilson while the camera is focused on him. This was meant to lead into a scene which was deleted about the police being called to the neighborhood for an unrelated issue but end up discovering Bob's marijuana crop.