$("span:contains('FIND ME')")
ETA:
The contains selector is nice, but filtering a list of spans if probably quicker: http://jsperf.com/jquery-contains-vs-filter
$("span").filter(function() { return ($(this).text().indexOf('FIND ME') > -1) }); -- anywhere match
$("span").filter(function() { return ($(this).text() === 'FIND ME') }); -- exact match