Windows Desktop Search (WDS) 3.0 has been released to the web. You can download it from one of the following links (depending on your OS version):

Why doesn't Windows Vista appear in this list? Because the stuff that ships in WDS 3.0 is already built-in to Windows Vista - there's no need to install it. 

So if you're targeting Windows Vista (which I hope you are :-), why should you care? You can think of WDS 3.0 as a "redistributable" for the Windows Vista "Visualize, Search & Organize" features that go down-level (e.g. the indexing platform, the property system, the OLE DB Provider for Windows Search). This enables you to target these features and still run on Windows XP, with the addition of WDS 3.0. Examples of applications that do this are Outlook 2007 and OneNote 2007.