Lync Mobile client is finally available for download, at the moment only for Windows Phone.
I expect the Android, IOS and Symbian versions will follow shortly.
I haven't seen a press release yet, and the site hasn't been updated yet, but when the press release shows up, I will update this post.
Note that before you can run Lync Mobile on your mobile, you need to implement changes on your corporate Lync environment.
Lync Mobile for WP7 can be downloaded from here : http://www.windowsphone.com/en-US/apps/9ce93e51-5b35-e011-854c-00237de2db9e?wa=wsignin1.0