Each presenter uploads one programme each week on Friday and they are then available all week till the next one takes its place. You need "RealAudio Player" to listen to them although other programs might also do the job.
What's the web address, Michael? I've been missing Midwest Irish Radio online for some time now ... Tommy was one of their presenters (and may still be for all I know). I'd be happy to give Shamrock a try if someone lets me know where it is.