Official Website: http://my.nintendo.com/
My Nintendo is the latest version of Nintendo's customer rewards program, though (as far as I know) it's the second incarnation of My Nintendo in America. The original version of My Nintendo can be viewed on Internet Archive. Sometime after the seventh generation of video games started, My Nintendo was closed and replaced with Club Nintendo by the end of 2008. And now we've gone full circle with Club Nintendo ending last year and being replaced with the returning My Nintendo this year.
The new version of My Nintendo will allow you to earn Platinum and Gold Coins by buying digital games (including digital versions of retail games), playing Miitomo, signing onto Miiverse, and signing onto the Nintendo eShop on Wii U or 3DS. You can redeem the coins for various digital offerings and coupons. These rewards range from digital games and apps, discounts for certain other digital games (including digital versions of retail games), Miitomo offerings (costumes and tickets), and 3DS Home Menu Themes.
Now for some new news. Some reward offerings have had their availability period extended:
Some news sites have also said the Zelda Picross and WarioWare game have had their availability periods extended as well, but some readers say those games have always had the same availability period -- ie nothing has changed.
If there's any new My Nintendo news, feel free to bump this thread with them!