A little program I found that works great!
Check out www.orb.com. Download the program on your PC and then on your PC transfer video and/or music files into the designated folder you select (usually defaults to the "My Documents" folder).
On your Wii, go to https://mycast.orb.com/orb/html/index.html and login. After that, navigate on the mycast page to the folder on your PC where you transfered your video and music files into. Once you find the folder, stream away!!!
I've tried it and it works. Enjoy!