Streaming audio and video are media you don't have to wait to finish downloading before you can listen or view. While sites like The Daily .WAV are fun to get sounds to play on your computer as system events, longer .WAV files take too long to download and you can't listen to them until they're finished. With RealAudio, RealVideo and now with Microsoft's entry NetShow (renamed the Windows Media Player within the past two weeks), you can experience media in real time while it streams to your computer.
Streaming media is in a state of flux right now. For some time RealNetworks has dominated the field with the RealPlayer, which has been getting progressively better at playing audio and video. A year or so ago, Microsoft's NetShow began to compete with the RealPlayer. NetShow uses a different file format than RealPlayer, so you couldn't play a Real file on NetShow or play a NetShow file on the RealPlayer. Since this past Spring things have changed. W3C has released its recommendation for streaming media, SMIL 1.0. Microsoft has released the Windows Media Player, which now plays RealAudio files. RealNetworks is preparing to release the RealPlayer G2, which will be another step forward for streaming media (I'm not sure if the new RealPlayer will play Microsoft-formatted files).
The Good NewsThe good news is that you can stream RealAudio for free. RealNetworks has released a freeware version of the RealEncoder, the program that will convert .WAV files into streaming RealAudio files or convert live audio (through a microphone or line input) into RealAudio files. The encoder will also convert video files, but I believe you need the right video card (and of course a camera that connects to your computer) to make it work.
I've used the RealEncoder to make streaming audio files for the Registrar's home page at the University of Richmond, for the VACRAO WebWatch page, and for my John Milton: The Milton-L Home Page (where I've just begun recording Paradise Lost).