SO jQuery Fiddle
Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5
by Nick Craver
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
JavaScript
var src = "bla blaaa blaaaaaa 1 http://yahoo.com text something about and. http://www.google.com";
var match = src.replace(/http:\/\/([a-z0-9.-]+)/g, '<a href="$1">$1</a>');
alert(match);