title: What are the "must have" jQuery plugins?
body: <p>I'd like to know what are the most useful JQuery plugins. I'm particularly interested in  those which are likely to be useful in general UI development, such as <a href="http://tablesorter.com" rel="noreferrer">Tablesorter</a>, rather than those which serve uncommon needs.</p>
  
  <p>If you could provide a very brief description of the plugin's purpose, that would be really helpful.</p>
  
  <p>Thanks,
  Don</p>