It’s Feb 2013, and I can now target XP in VS2012 by setting:
Project Properties -> General -> Platform Toolset to:
Visual Studio 2012 – Windows XP (v110_xp)
You will have to redistribute the msvcp110.dll libraries et al with your application, which are found here: "<Program Files>\Microsoft Visual Studio 11.0\VC\redist\x86\Microsoft.VC110.CRT\"
Update Aug 2015 with Visual Studio 2015
There seems to be quite a selection now. I was able to compile application in VS2015 using Visual Studio 2015 – Windows XP (v140_xp) setting. To make it actually run on Win XP I had to deploy (copy alongside application) msvcr100.dll for Release build and msvcr110.dll and msvcr100d.dll for Debug build (note there is a difference in numbers 100 and 110, also debug lib msvcr100d.dll may not be redistributable)
