Microsoft CEO Steve Ballmer apparently referenced company plans to make
phones in a memo sent to employees about the recent MS re-org,
according to All Things D. 
The WSJ-spinoff tech blog published the full content of Ballmer's reorg
memo to his minions, which included the following mobile-oriented bit
in a pargagraph focusing on competition from Apple:

"Today, we?re changing the way we work with hardware vendors to
ensure that we can provide complete experiences with absolutely no
compromises. We?ll do the same with phones?providing choice as we work
to create great end-to-end experiences."

Ultramobile blog JK on the Run added some fuel to the story's fire by publishing a
credible but anonymous tip about Microsoft holding meetings regarding
the mythical Zune Phone, a would-be musicphone competitor to Apple's
own iconic handset:

"This source had information about a meeting this week in Redmond that
was planning a Zune phone to compete with the iPhone.  According to
this information the Zune phone will be based on a specialized variant
of Windows Mobile 7 and key functionality will be centered around
WIndows Live Services.  On the hardware side the ZunePhone would be
touch-screen based using multi-touch (surprise) but other than that not
much is known."

Given Microsoft's recent acquisition of Danger - the creators of the
original Sidekick and the Sidekick OS - it certainly makes sense that
the one-time King of Software would be working on a new mobile device
platform.  Smartphones certainly aren't a dying breed, but the action right now is in the "consumer
smartphone" space - that is, high-end multimedia phones with advanced
messaging and entertainment features running on easy to use platforms
tuned for consumers, and not necessarily business/power users.

While I personally don't know how well a Zune Phone would sell, I'm
certainly all for a Danger-designed new version of Windows Mobile.  It
might be a bit much to expect another Sidekick-style major innovation
from the Danger kids, but they certainly have a good track record when
it comes to designing mobile devices.  Can they work their magic once
more under the giant corporate umbrella of Ballmer & Co?  We shall
see.