SELECT * FROM `table` WHERE 
(
    (
        UNIX_TIMESTAMP(created)
        >
        (
            UNIX_TIMESTAMP(
                STR_TO_DATE(
                    CONCAT(
                        YEAR(
                            NOW()
                        ), 
                        '-', 
                        MONTH(
                            NOW()
                        ), 
                        '-', 
                        DAY(NOW()), 
                        ' 00:00:00'
                    ), 
                    '%Y-%m-%d %H:%i:%s'
                )
            ) - (24 * 60 * 60)
        )
    )
    AND
    (   
        UNIX_TIMESTAMP(created)
        <
        (
            UNIX_TIMESTAMP(
                STR_TO_DATE(
                    CONCAT(
                        YEAR(
                            NOW()
                        ), 
                        '-', 
                        MONTH(
                            NOW()
                        ), 
                        '-', 
                        DAY(NOW()), 
                        ' 00:00:00'
                    ), 
                    '%Y-%m-%d %H:%i:%s'
                )
            )
        )
    )       
);

15.06.2011