Everyone should start emailing Nintendo to create the Wii Demo Channel and the Wii World channel.
If you combine your Wii with a 2GB SD card there is plenty of room for demo's, especially becasue the games are lightweight compared to something like Xbox 360s/PS3's "HD" demo's.
Also, I heard a rumor that Nintendo will add support for USB external HDD's in the future.
The more people hound them, the quicker it could become reality. Just and idea.