I'm not sure how many people here will care, but I figured I'd mention this anyway. On June 27th, the WiiConnect24 service will go offline. After this date, the only thing that will remain is actual online play; all channels and game features that used this service will no longer be usable.
The following is a list of channels that will no longer function after the shutdown:
News Channel
Forecast Channel
Nintendo Channel
Check Mii Out Channel
Everybody Votes Channel
Mario Kart Channel
Wii Message Board
The following channels will have reduced functionality:
Mii Channel - No longer able to send and receive Miis.
Wii Shop Channel - No longer able to send out gifts.
The following are the games I can think of that will lose the listed features:
Animal Crossing City Folk - No longer able to send mail to other towns.
Boom Blox - No longer able to send and receive created puzzles.
ExciteBike: World Rally - No longer able to send and receive custom tracks.
ExciteBots: Trick Racing - No longer able to send and receive replays.
Mario Kart Wii - No longer able to send and receive ghosts, view leaderboards, or play tournaments.
Metroid Prime 3: Corruption - No longer able to send and receive friend vouchers.
Metroid Prime Trilogy - No longer able to send and receive friend vouchers.
Super Smash Brothers Brawl - No longer able to send and receive pictures, replays, and stages.
Wii Music - No longer able to send and receive created music