A lot of people have been inquiring about multicast streams and just what's available out there.
The best client I've seen for receiving SAP announced multicast streams is VLC (http://www.videolan.org/vlc/) which appears to be quite capable in terms of video formats, frame buffering and decoding capabilities across multiple operating systems.
GRNet has a good script for decoding the source addresses for current multicast stream- think of it as a channel tuning guide. Just remember that this is from a Greek perspective so may not mirror 100% the SAP announcements available on your particular network, but is generally pretty accurate.
How do you know you're on a multicast enabled network? Good question! There are a couple of very useful utilities available to gauge network connectivity (network provision from AARNet is a very good start, along with adequately configured routers). Internet2 Detective is one of these applications and is available through Java Applets, Mac OSX widgets and standalone clients. Also available is the SURFnet detective, which takes a slightly different view of network connectivity (Windows and Linux only) and also allows customisation of the client. These tools not only check for multicast IGMP connectivity, but also whether IPv6 addresses are completely resolvable from your location. Very useful!