Nintendo has just released the beta version of MiiVerse for web browsers. You can get to it on either your smart phone or PC via http://miiverse.nintendo.net. Here is the announcement post from Tom:
Hi, it’s Tom at Nintendo. Miiverse is now available on the web! Starting right now, you can check out Miiverse from PCs and smartphones. Just go to this url and log in with your Nintendo Network ID and password: https://miiverse.nintendo.net This part of Miiverse is still in beta so the experience will be different from what you’re used to on Wii U. You’ll still be able to comment to posts, check out communities, and give Yeahs, among other features. This means you can take Miiverse on the go, so you’ll never have to be away from it again. Enjoy!