Upgrades to the CBS-owned music platform allow users to add songs or artists to their online libraries with one click and post instant music recommendations. Music charts in member profiles will also be updated immediately to reflect new song plays from its catalog of 5 million tracks.

As of Thursday, however, the new site appeared to be slow--possibly from a surge in traffic. A Last.fm spokesperson could not be reached for comment Thursday.

Going beyond the Web, the company this week released a Last.fm application for the iPhone and recently partnered with Logitech to give listeners access to the service via their home stereos. CBS is also promoting Last.fm through a campaign that directs viewers of the network drama "Swingtown" to go to a Last.fm page featuring playlists of songs featured on the show.

The site redesign is only the latest in a series of steps to build out the U.K.-based social music service since CBS acquired it for $280 million last year. Most recently, Last.fm formally unveiled a new program that pays royalties to unsigned or independent musicians and bands.

In May, the site launched a new video channel showcasing both established and emerging bands as well as original programming. Last.fm also struck a deal that month to power AOL Radio in Europe. CBS also assumed full responsibility for ad sales at AOL.