Version 1.1

All the aspects of the API that were added, or had a new signature added, in the corresponding version of jQuery.
jQuery 1.1 Release Notes.

jQuery.ajaxSetup()
New in 1.1! Low-Level Interface
Set default values for future Ajax requests.
.attr()
Attributes, General Attributes
Get the value of an attribute for the first element in the set of matched elements.
event.data
New in 1.1! Event Object
An optional data map passed to an event method when the current executing handler is bound.
.one()
New in 1.1! Event Handler Attachment
Attach a handler to an event for the elements. The handler is executed at most once per element.

jQuery API