Have a look at
Windows Media Encoder and
Real Producer. These will both let you stream video/audio from your site, and both are free.
You can also use Quicktime to stream movies, but, TBH, while I am generally a big fan of Quicktime, it does not do a good job of streaming. I have also never found any freeware encoding tools (in fact, the only tools I know of that can encode QT streaming video are
Discreet's Media Cleaner and Sorenson Broadcaster - neither of which are cheap).
Anyway, with either of those, you will be able to stream data from your website. It might also be worth asking if your webhost has a dedicated streaming server, If you use one of these, and tell WM Encoder or RealProducer to encode multiple bitrates, the server will automatically send the appropriate bitrate for the current network connections.
Of course, another option (if you have Flash MX Pro 2004) is to import the video into Flash and export it as a Flash movie (this actually works well).