If you are running Windows, I have found Rip Edit Burn from Blaze Audio to be excellent. You can use it to record, edit, and convert files. Program is reasonably priced. You do have to download a free encoder if you don't already have one. I use LAME and have had no trouble creating great sounding recordings of streamed audio. You can purchase at this site. The site will also direct you to the free encoder options to download. Easy installation, easy operation.
http://www.blazeaudio.com/
As far as the MAC goes, I have heard that Garage Band will also record live streams but I havent' been able to figure out how to do that.