Dialog modality curtains should fade in and out.
Dialogs should slide down and slide back up when done.
(Such as editing a user in security app)
Confirmations should fade in with a slight zoom and fade out with a slight zoom out.
(Such as delete confirmations)
Notifications should slide down from the top - and fade out when done.
Transitions can be implemented with css3 animations.
These transitions are very simple and can be implemented simply by applying css styles.