"Web Media" is MC's list of streaming radio stations. Sadly, it is typically out-of-date, and it's interface (which is a bit clunky in my opinion) has not been reworked in a LONG time.
To listen to Shoutcast stations, however, what I do is to simply use the Shoutcast website's "Tune In" links, and to set the system up to automatically use MC to play the streaming files. This way, all I do is click on a Tune In link, and MC starts playing the stream. Since shoutcast tends to keep their list fairly up to date, this works well EXCEPT for the fact that you can't (as far as I know) keep "favorites" on the website.
If you want to have certain stations that you listen to all the time be more easily accessed, you can actually add them to the MC library and tag them as if they were songs. They'll appear in the Panes just like songs do, but they'll be streaming links. I tag them with the genre "Web Radio," and use the "Artist" field to define the genre (i.e. "Web Radio - Blues," "Web Radio - Rock" etc.) and the "Album" field to define the name of the radio station. This may seem a little odd, but when you see it in MC, it makes complete sense and it works very well. You select "Web Radio" in the genre pane, then the Genre of stations in the next pane, then the actual radio station in the third pane. Even though the names of the panes aren't right, it's very intuitive when you use it.
The only problem with this setup is that web radio stations tend to come and go, so many of the links you save will eventually stop working. This, however, is a problem with the internet radio stations in general.
Larry