Here's the info direct from Nintendo:
The Wii™ console will revolutionize how people play games. But more importantly, it will entice new players into the world of video games by offering a variety of entertainment, information and communication Channels that add value to the console and make it a device that the entire family can enjoy. The Wii Channel Menu will be the first screen shown on the television, as it easily integrates itself as part of people’s everyday lives.
Disc Channel: This channel allows users to play either Wii game discs or the entire library of Nintendo GameCube™ discs.
Mii™ Channel: Fun caricatured portraits created in this channel can be used as characters across a variety of Wii software. Portraits can be stored in a user’s Wii Remote and taken to a friend’s house to play on another Wii console. Each member of the family can have his or her Wii Remote personalized with a caricature.
Photo Channel: This channel allows users to take digital pictures stored on an SD memory card and display them on their television screens. Users also can manipulate the photos in a variety of fun and creative ways, such as zooming or creating mosaics, puzzles or slide shows. They can draw, add stamps, and copy and paste. They also can change the “mood” of photos by brightening them, converting them to monochrome, inverting the color or changing them to stark black and white. Users can even add an MP3 tune to their slide shows. It provides a fun and easy outlet for people to edit their digital pictures. Users also can send their pictures to other Wii consoles by attaching a photo to the Wii Message Board.
Forecast Channel: Users who have connected their Wii console to the Internet can access free local weather forecasts just a few seconds after turning on the Wii console. The WiiConnect24™ service automatically updates local weather information. Users can view forecasts for cities around the world on a 3-D globe.
News Channel: Users can access breaking news with the touch of a button. When connected to the Internet, the WiiConnect24 service automatically updates this free channel and organizes it in a variety of topical categories. Users can see where news is happening by viewing the location of news stories on a 3-D globe.
Wii Shop Channel: This is where users go to buy Wii Points or redeem them to download classic video games to the Virtual Console™. Users also can use points to download the Opera browser used in the Internet Channel.
Internet Channel: This channel dramatically changes the relationship between a user’s home, the television and the Internet. Users download the Opera browser with Wii Points. Then they can surf the Internet right from the comfort of their couch. They can do quick research while watching a television program (“What was that actor’s name again?”). Or book travel plans and shop during commercials. The service is compatible with Macromedia Flash.
Wii Message Board: Forget hand-scrawled notes tacked to the refrigerator door. Users can leave messages for other family members on a calendar-based message board. They also can use WiiConnect24 to send messages to people outside the home as well. Even better, people can trade photos and text messages with cell phone users. The service also allows for incoming messages targeted at software, such as a new map or weapon for a game. Games can constantly be updated, thereby extending their playability.
Sounds very interesting! You can see these channels in action by following the link below