While most radio stations are looking for ways to expand their online presence, CBS Interactive Music Group is doing the opposite with social music site Last.fm, says Paid Content.

CBS will broadcast the streaming service on the company’s HD multicast stations. Last year Last.fm became part of CBS.

Last.fm will effectively take over CBS HD broadcast stations starting in New York, Los Angeles, Chicago and San Francisco. The broadcasts kick off on Monday, October 5. The broadcast will feature a mix of music influenced by the service’s user-generated weekly charts along with live performances and interviews.

Listeners will be able to access the station through the Last.fm site as well as CBS Radio and Yahoo Music radio sites as well as mobile apps for the iPhone, iPod Touch and certain BlackBerrys.

David Goodman, president of the recently formed CBSi Music Group, told paidContent that CBS will devote more resources toward promoting HD radio in general, something that could give Microsoft’s upcoming Zune HD devices a boost as well. The Zune HD will go on sale September 15, with 16GB and 32GB models, priced at $219 and $289, respectively.

Meanwhile, Apple’s new iPod nano features an FM receiver enabling radio’s 235 million weekly listeners to have another way to listen to radio, says Radio Online. The new unit will also offer live pause capability as well as iTunes tagging.

The radio tuner allows users to tag songs they hear on the radio, sync them with their iTunes, and identify the song’s artist and title and purchase it from the iTunes store via the Radio Advertising Bureau’s “Buy From FM” platform, explains Ad Age.

Jeff Haley, CEO of the Radio Advertising Bureau, “The idea that an 85-year-old medium has the chance to remain relevant and capture new distribution in an environment when those things are hard to come by is very exciting.” In addition to Buy From FM, the FM tuner could also enable radio stations and advertisers to tag their radio ads to become interactive through the MP3 platform.

The industry’s largest company, Clear Channel, has also made significant in-roads in bringing radio to iPhones and BlackBerrys, and this week just rolled out the 2.2 version of its iheartradio application for 300 of its stations. The app amassed 2.5 million unique listeners by June, with streaming radio helping to increase Clear Channel’s cumulative audience by 15%.