Are the users still in the usergroup "Users Awaiting Email Confirmation"?
If they are, then the cron job set by vb should be sending out that email, than again in 5 days.
You can put this in a Notice and display it only to that usergroup or you can send out a email with this link:
Code:
<if condition="$bbuserinfo['usergroupid'] ==3">
<td class="vbmenu_control"><a href="register.php?do=requestemail">Resend Activation Email</a></td>
</if>
Code:
http://yourdomainhere.com/forums/register.php?do=requestemail