Some people have upgraded their wii to 4.0 before installing the homebrew channel. Now as most people know, the Twilight hack no longer works in 4.0. So a new way is needed!
Step 1: Things You Need:
1. a wii
2. a SD card
3. a pc with internet access (of course)
Step 2: Action!
Go to http://bannerbomb.qoid.us/ and download the new bannerbomb exploit.
Follow all of the bannerbomb instructions and you will have the home brew channel on your 4.0 Wii!!
If this doesn't work for you, I'm sorry but you'll have to wait for a new exploit.
What can you do with the homebrew channel you ask?
Play games, play video and audio, and various other activities!
More information can be found here: http://www.wiibrew.org/wiki/Main_Page
Do not pay for homebrew or the homebrew channel
If you have a wifi enabled Wii I suggest: http://www.wiibrew.org/wiki/Homebrew_Browser