Ina Fried is reporting that Messenger 7 for Mac is now available for download.  According to the Mactopia website, the new Messenger for Mac is designed for use on either older PowerPC Macs, or the newer Intel ones:

Messenger for Mac 7 is an integrated communications client that enables you to communicate with contacts within and outside your organization. Messenger for Mac 7 is a Universal application that is built to run on both PowerPC-based and Intel-based Macs and makes it easy to take advantage of the full power of real-time communications.
For personal Windows Live account users, Messenger for Mac 7 includes the following new features:

• Customize your contact list with nicknames that you choose
• Use Bonjour to see other Messenger for Mac contacts who are online and near your location
• Search for contacts in your personal contact list