In Windows 7 you can create and add your own federated search providers for use in Windows Explorer. A while ago I published a step-by-step guide on how you can build federated search for a SharePoint site or for your favorite web site. The article is available in its full (in Swedish) at tipsomvista.se.
About Author
Andreas Stenhall
I'm Andreas Stenhall and my work passion is the Windows client in combination with Microsoft 365 security and management services. I do consulting, I produce and teach my own courses, I lecture and I present and my formal work title is prinicipal workplace advisor and architect at Coligo in Stockholm, Sweden. I'm also proud to be an Microsoft MVP since 2009. I have presented at BUILD, TechEd in the US and Europe and regional TechDays. Follow me on twitter @AndreasStenhall.