I've always disliked the way that when you mass email some users (users selected based on criteria you specify), you only saw the userid of each user emailed, and not their names. For some reason, I've always been curious to know who it was exactly that was getting emailed. So I did this little hack...honestly, it's so simple, it probably isn't worthy of being called a hack.

All you have to do is edit the file in the admin directory email.php.

Around line 152, look for this:
echo "$user[userid]<br>\n";
And replace it with this:
echo "$user[userid]: $user[username]<br>\n";
Upload the edited file, of course, and that's it!