Where is the latest Microsoft Messenger (or alternative) that works with Exchange? I'm using Microsoft Messenger for Mac 7.0.2, but it crashes every time the network connection is lost and has to be force quitted. I'm looking for an alternative that is more stable.

It seems Microsoft Messenger has been discontinued in favor of Skype. I downloaded Skype but can't find a way to sign into my Exchange account at work. Is it possible to use Skype with an Exchange account? If not, is there somewhere I can download Microsoft Messenger 8.0 / 2011?
Lync for Mac may be what you're looking for. It's a replacement for Office Communicator (the IM, presence, conferencing and voice client). Your work environment should support it with the server though.