Any way to extract music from Nintendo Wii Games?

You might try first looking to see if there are composed albums of the sound track. You'll be endorsing the availability of the music separate from the game (many already are sold as MP3s, but a CD is still easier to rip than extracting from a game) which hopefully will entice publishers to make the sound tracks for other games available for sale as well.

examples:
Super Mario Galaxy 1 & 2
A Boy and His Blob (to be released "soon")

Is it possible? For some games it is, but it can't be a general "yes". Not all games use the same music format, so it depends whether someone has already programmed a decoder/player for the specific game's format.

vgmstream can play many formats, so you can probably give that a shot. You'll have to locate the music files on the game disc though, which may itself be a difficult task.