"On hold", "Set aside", and "Later"The following might also be good headings if you're looking for something less formal:
On hold-- Paused. Connotations that the event/task is ready to initiate or resume and has been intentionally postponed. (Also used to describe a state of interminable limbo hell on the telephone.)
Set aside-- Removed from the focal point. Similar to cast-off, trashed, or discarded, but holds the possibility of the item/task being restored to its former place. (Can also describe when something is saved or reserved for a special purpose.)
Later-- As opposed to right now. This one doesn't indicate that the task has already been started as well as the other two do.
All along the same lines as @Chris Sunami's popular "Postponed".