Nintendo has launched the promised browser-based version of Miiverse. You can check your notifications and Miiverse announcements, view your activity feed and profile, and explore communities. You are also able to "Yeah!" and reply to other member's posts (text only) but it does not appear to be possible to create a brand new post.
I know I'll be checking out Miiverse a lot more now. I'm too lazy to turn on the Wii U just to look at Miiverse looks like you can link to specific posts too. I like it! I can't wait for the 3DS one, especially if 3DS games have their own communities.
Seems like you can reply to posts but not make new posts? Unless I'm missing something.