I was surprised that I hadn't seen anything on the forum about Cube World, but the Alpha was released a few days ago. It is an infinite world, voxel based RPG. Currently just for Windows, although a Mac version is planned.
Unfortunately they have been struggling with the demand for the game, so no new user registration is being allowed at the moment (you need to have an account with them to buy the game, similar to Minecraft), but they are expecting that to stabilize over the next few days.
From the website:
I'm Wollay, the creator of Cube World. I started this game in June 2011 as a hobby project. My inspirations were Minecraft, Zelda, Secret of Mana, Monster Hunter, Diablo, World of Warcraft and many more. My aim was to create an infinite, colorful, procedurally generated world, full of adventures, monsters, and mysteries. The result is Cube World, a voxel-based role-playing game.
My wife joined development in 2012, and we're planning to release analpha version for Windows PC soon. The alpha already has many features, but some are still missing. You can check out a feature overview below.
The alpha will be available for a lower price than the beta version and the final version. We're planning to release updates regularly. Updates are free.