I've searched here but haven't found the following:

Adding the private message button and link to the Members List so you could pm someone right from the Members List. Of course, it would only show up if the person had checked to allow for private messaging.

Does this hack already exist?

Sounds like a template modification to me. I was able to do so myself just editing the memberlist and memberlistbit templates, using some info I got out of the User Info display templates to get an individual member's PM info.

Thank you, I will see if I can figure it out!

The code you want is...

After <a href="member.php?s=$session[sessionhash]&action=getinfo&userid=$userinfo[userid]">$userinfo[username]</a>

Add

$userinfo[pmlink]

This will add the PM button next to their name.

You might want to think about making it look prettier, but that's the code you need.

Aren't you great! Thanks for that! :)