What Yammer clients available on the Mac?
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.