I just learned about Sonlger, an application designed by Martin Millmore which brings Spotify into the Windows Media Center desktop software. In a post on The Digital Lifestyle blog, blogger Ian Dixon notes that a recent update to the app now adds in Last.fm integration, too.
Once installed, Songler gives you access to the 6 million tracks hosted on Spotify’s streaming music service. The tracks are searchable by artist, album, or song name. Now with the new Last.fm integration, you can scrobble the tunes you listen to using Spotify back to your Last.fm account, too. You can also stream Last.fm stations directly in Media Center.
Songler is available as a free download from the (unofficial) Windows Media Center app store at madeformediacenter.com.