Anyone know of a program that will allow me to record sound playing on my computer?

As some of you know I have a radio show. This radio show also streams online. As of late ive been having musicians come onto my show and play live. I was thinking it would be nice if I were able to somehow record the show on my comp and give copies to the musicians. Anyone know of a program that will allow me to record the audio playing through my comp?

Thanks :)