The Flip4Mac people have done an admirable job. However, they are still having problems with some streams. Like Bob v, I couldn't get the WIBC stream to work with Flip4Mac.
However, Microsoft's website still has a link to their, now discontinued, Windows Media Player. Here
It has some success with online streams where Flip4Mac still fails.
[Update: 11/09/2006 - It works now. I'm thinking I didn't understand that I had to click on the Play button to get the stream to start. I'm used to the stream starting by itself.]