People in my new job seems to like Yammer. I'm aware that Yammer has a desktop client for the Mac, but I find the interface rather unappealing (version 300222 of the Adobe Air client is not responsive and really slow when switching between my primary network and external networks). I wonder if there are 3rd party clients available?
There are two out there that I like, each for different reasons:
Gabble is a free application that allows for threaded conversations, private and public groups, attachments, and tags.
Scuttlebutt is an application in beta. The major thing that it improves over Gabble is support for multiple Yammer accounts (although there is a workaround for that in Gabble: you can launch multiple Gabble instances).
Both of these software are native OS X apps and should be much faster to use than an Adobe Air client as well as have the potential to support things like spelling services, voice dictation and other nice integrations that a native app can provide more easily than using a cross-platform toolbox.
There is Gabble, you can download from here: