jQuery('div.panel')
    All divs with class=“panel”
jQuery('p#intro')
    The paragraph with id=“intro”
jQuery('div#content a:visible')
    All visible links inside the div with id=“content”
jQuery('input[@name=email]')
    All input fields with name=“email”
jQuery('table.orders tr:odd')
    “odd” numbered rows in a table with class “orders”
jQuery('a[@href^="http://"]')
    All external links (links that start with http://)
jQuery('p[a]')

http://simonwillison.net/2007/Aug/15/jquery/

Elements selection in jQuery

jQuery