Element Data in jQuery

Added in jQuery 1.2
Attaching data to elements can be hazardous.
Store data: jQuery.data(elem, "name", "value");
Read data: jQuery.data(elem, "name");
All data is stored in a central cache and completely garbage collected,
as necessary.

Added in jQuery 1.2.3
Can handle namespacing:

$("div").data("test", "original");
$("div").data("test.plugin", "new data");
$("div").data("test") == "original"; // true
$("div").data("test.plugin") == "new data"; // true

Advanced data handling can be overridden by plugins:

$(element).bind("setData.draggable", function(event, key, value) {
self.options[key] = value;
}).bind("getData.draggable", function(event, key) {
return self.options[key];
});