Ahi va el script que uso. !
Código PHP:
function url($text){
$text = html_entity_decode($text);
$text = " ".$text;
$text = eregi_replace('(((f|ht){1}tp://)[-a-zA-Z0-9@:%_+.~#?&//=]+)','<a href="\1">\1</a>', $text);
$text = eregi_replace('(((f|ht){1}tps://)[-a-zA-Z0-9@:%_+.~#?&//=]+)', '<a href="\1">\1</a>', $text);
$text = eregi_replace('([[:space:]()[{}])(www.[-a-zA-Z0-9@:%_+.~#?&//=]+)', '\1<a href="http://\2">\2</a>', $text);
//$text = eregi_replace('(@([0-9a-z][0-9a-z-]+.)+[a-z]{2,3})', '<a href="site.com/profile?u=\1">\1</a>', $text);
return $text;
}