TheDailyWTF.com has an interesting article titled Anatomii of a Hack which looks at the process by which the homebrew scene has been getting into the guts of Nintendo's super-popular console:

Wii hacking for the consumer isn't hard to do, as instructions are readily available online, and the only necessary supplies are an SD card and Twilight Princess. Homebrew applications include media players (including DVD playback, not natively supported by the Wii), emulators, games (originals as well as Quake and Doom), file system browsers, and a version of Linux (surprised?). There's even a utility to change the Wii's region, which is now being used for buying (yes, buying) WiiWare games that haven't been made available to all regions.

For the most part it seems that the homebrew scene caters to the geeks who want to see what they can do with the system. Sure, there are those that use these powers for evil, but the intentions of the majority of the community are pure. The Wii isn't just a games console, it's an interesting challenge that has brought people together for little more than the joy of hacking, experimentation, and creation.

Bit more on the technical side of things but it's a good read and gives some insight into the ongoing battle between the modding community and the corporate overlords that want to prevent it.