"Is SQL Server version X supported on hypervisor platform Q?" or something even more specific like "Is SQL Server 2012 supported on VMWare vSphere ESX 4.1 Update 2? Or do I have to upgrade to ESX 5.0?".
Now, when I'm asked a question like this, I usually drool and act like an ape, hoping the the questioner will flee in terror. If they insist on hanging around to hear a real answer, I now refer them to the Windows Server Catalog site thanks to a tip from my NASCAR buddy and Microsoft MVP, Geoff Hiten (Twitter | Blog). For some reason, this very useful site is unknown to most - but it provides the most up-to-date and comprehensive information on what Microsoft supports. Once you've determined which hypervisor you want to check for support, you can simply search the site for your area of interest, say “Microsoft Server Virtualization Validation”.
Since Microsoft certifies OS's for virtualization platforms, you can by extension be assured that any supported application for that OS is also supported on that virtualization platform. So, to answer the early question about VMWare VSphere ESX, you'll find the entry for VMWare VSphere ESX 4.1 (Update 2) at http://www.windowsservercatalog.com/item.aspx?idItem=698bb582-b1ca-7124-05e4-256558d39e68&bCatID=1521.
Now, you know the rest of the story about why I drool and make monkey sounds at some conferences. That's my story, and I'm sticking to it.