Are you using MySQL, if so have you tried adding ORDER BY RAND(); to select the item randomly. I'd try something like this:
$q1 = "Select distinct user from users";
$result=mysql_query($q1);
while($row = mysql_fetch_array($result)) {
$tmp_user = $row['user'];
$q2 = "Select item from items where user='$tmp_user' order by rand(); limit 1";
$result2=mysql_query($q2);
$row2=mysql_fetch_array($result2);
$item = $row2['item'];
echo $tmp_user." has item ".$item."<br><br>";
}
Not necessarily the tidiest way to do it, but it should achieve what you are looking for. You may not need 'distinct' user if the user is only in the user table once.
HTH - Blu