mysql> CREATE TABLE `t1` (`id` int(11) NOT NULL auto_increment,`name` varchar(20) default NULL,`today` date default NULL, PRIMARY KEY  (`id`)) ENGINE=MyISAM;


mysql> DELIMITER //
mysql> CREATE TRIGGER t1_date BEFORE INSERT ON t1 FOR EACH ROW
    -> BEGIN
    -> SET NEW.today = CURRENT_DATE;
    -> END //
mysql> DELIMITER ;

mysql> insert into t1 (name) values('bob'),('joe'),('dean'); 
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0
mysql> select * from t1; 
+----+------+------------+
| id | name | today      |
+----+------+------------+
|  1 | bob  | 2007-11-16 | 
|  2 | joe  | 2007-11-16 | 
|  3 | dean | 2007-11-16 | 
+----+------+------------+
3 rows in set (0.00 sec)