You can find the new channel in the Wii Software section in the Wii Shop Channel.
On the Wii Shop Channel news frontpage, you can read the following:
To celebrate the upcoming launch of Metroid Prime 3: Corruption for Wii on October 26, we have two special treats for you on the Wii Shop Channel!
Metroid Prime 3 Preview
The Metroid Prime 3 Preview is available to download now, for free, from the Wii Software section.
Through the Channel, you’ll be able to view never-before-seen videos of Smus Aran in her most intense mission yet. New vidoes will be added in the run-up to the game’s release, so to keep checking back for more!
Super Metroid (Virtual Console)
This 1994 Super Nintendo classic sees Samus Aran return to Planet Zebes to stop the Space Pirates and eliminate their leader Mother Brain once and for all. Luckily, Samus is more tooled-up for action than ever before.
Super Metroid introduced many features that would become standard in the Metroid Prime seires: abilities likethe Charge Beam and Grappling Beam, and the on-screen map system that helped players navigate the massive game world.
Super Metroid is truly a landmark moment in Metroid – and video game – history.