Nintendo opted to let online go for Wii and DS games, but that hasn’t held back fans. Today fans have unveiled homebrew servers to play select Wii and DS games with other players online.
To get this to work, you need to have a digital copy of the game, and no, these aren’t DSi or WiiWare games. Presumably you used homebrew tools to make your backups, and use certain devices to play those backups as well. They haven't brought everything back and make it work like before quite yet, but you can rest assure the fans will do their best, well, if Nintendo leaves them alone.
Right now, Mario Kart Wii, Super Smash Bros Brawl, and Endless Ocean are the only Wii games confirmed working for online play. The DS has a heck of a lot more! We’ll go through the big titles below:
Online play:
Advance Wars: Days of Ruin
Mario Kart DS
Metroid Prime Hunters
Tetris DS
Download content:
Professor Layton and the Curious Village
Professor Layton and the Last Specter
Professor Layton and the Diabolical Quest
Pokemon Diamond, Pearl, Platinum, Soulsilver, HeartGold, White, Black, White 2, Black 2
Picross DS
Style Savvy
Inazuma Eleven 2 – Firestorm and Blizzard
Warioware D.I.Y.
You can read the full lists here and here. Image is from Mario Kart Wii.