GROUP_CONCATを見てください
<?php
session_start();
require_once "common.php";
$sql = "SELECT *,GROUP_CONCAT(log.date) as login_date FROM user INNER JOIN log ON log.user_id = user.id INNER JOIN evalution ON evalution.user_id = user.id GROUP BY user.id";
$result = mysql_query($sql) or die(mysql_error());
?>
<table width="40%" border=1>
<tr>
<td>Log_Name</td>
<td>Login</td>
<td>Evalution</td>
</tr>
<?php
while($row = mysql_fetch_assoc($result))
{
?>
<tr>
<td><?php echo $row['name'];?></td>
<td><?php echo str_replace(",","<br/>",$row['login_date']); ?></td>
<td><?php echo $row['evalution']; ?></td>
</tr>
<?php
}
?>
</table>
GROUP_CONCAT(log.date)は、コンマ区切りの日付リストを返し、必要に応じて表示できます。