During their E3 2009 presentation, Microsoft announced that they'll be integrating a few social networks into Xbox Live. Among these is Last.fm, which is set to go live later this year.
As announced at E3, the Last.fm service will be free to Gold subscribers. According to Kotaku, the Last.fm section of the dashboard will function pretty much the same way as the web-based one.
Using it, Xbox 360 owners can browse artist and tracks, create and share playlists, create their own stations and check out artist pages for photos and band info. What hasn't been revealed yet is if whether Last.fm stations can be used as in-game soundtracks.
A specific release date has yet to be set as well, but in the meantime you can check out these screenshots to see how the new service would look like.