From the NPR website:
NPR will be the only radio broadcaster of the concert “We Are One: The Obama Inaugural Celebration,” the star-studded kickoff of official inaugural festivities, starting at 2 p.m. ET/11 a.m PT on Sunday, Jan. 18. The event, which is free and open to the public at the Lincoln Memorial in Washington, D.C., will be broadcast by NPR to public radio stations nationwide, and will be available as a simultaneous stream on this page and at the Web sites of many stations. For more information, find your local station by visiting NPR.org/stations.
To watch via cable and satellite stations, HBO will be making their signal available free of charge to any cable or satellite subscriber. HBO’s broadcast of the event will begin at 2:30 p.m. ET/11:30 a.m. PT and replay at 7pm ET/PT and 11:30 p.m. ET/PT.