Tommy has a weekly radio show devoted to Irish traditional/folklore etc, on Downtown Radio (Northern Ireland) which you can catch online at Downtown Radio, Saturday nights, 6-8pm. (Not sure if anyone's covering while he's in the states.)

His brother Colum also has a weekly Saturday night slot. Colum is on BBC Radio Ulster, 10pm-midnight. This can be heard live, online, or by using the Beeb's listen-again option, which keeps each program available for one week after going to air. Either way, the starting point for Colum is Radio Ulster.