On May 20, "certain online functionality" for various Wii, DS, and DSi games will be removed. This includes online gaming, matchmaking, leaderboards, download of free add-on content, and user exchange of in-game items.

Games affected include a very substantial list of games including Super Smash Bros. Brawl, Mario Kart DS, Mario Kart Wii, Pokemon Black and White, and countless others. In addition, Wii Speak, Wii Speak Channel, and the Wii mode on the Wii U will no longer function.

Access to the Wii Shop, DSi shop, and video-on-demand services will not be affected in this move.

The full (and it is a very, very large list) of games can be found over at Nintendo.