CBS Radio is to begin adding its streams to Last.fm, in the first real integration of the social music site with its new owner since the $280 million acquisition last May. CBS Radio says it will this spring launch a new player that will be added to Last.fm, offering stations like KROQ, WXRT and WCBS-FM to US users only. It compared the plan to its recent deal to power AOL (NYSE: TWX) Radio and to Last.fm’s relationship with BBC Radio. But we’re told the final picture of the integration is not yet determined. At the most basic, Last.fm users will get to ”scrobble” tunes they hear through CBS Radio, meaning they get to flag tracks to friends and add them to playlists.