I've just found this link to a website that enables you to stream media from your PC to your Wii ustilising the Opera browser.
Click for Streaming media on your Wii
If its on the same network it streams across your LAN if not its via the net, meaning you can use other peoples consoles if you are away from your own.
I've had a play and its working pretty well, photos, music, documents and video all stream pretty fast.
The only issue I've had so far is with the aspect ratio on my video files, they are getting squished vertically distorting the image, I'm sure someone will figure it out though.
On a side note, does anyone know how to hide the options bar at the base of the opera browser screen on the Wii? The one that you use to select your favourites etc. Its so god damn huge!
I'm pretty sure its partly to blame for my videos being crunched up.