I'd like to advertise the project which some friends and I started some months ago. Back then, we had the idea to create
a Minecraft-like game with destructible terrain, but without blocks. We made a prototype and it worked pretty well. It features an infinitely large procedural world and correct physics interaction with the terrain. Everything is written from scratch in plain OpenGL, currently supporting Linux and Windows. Here is some video footage:
For an overview of the technical details, have a look at this post on our blog.
We are currently rewriting the whole engine, with a long-term goal to create a game engine that allows easy creation of mods and games based on our terrain technology. The mid-term goal for the next year is to release a sandbox game with Minecraft-like gameplay.
We recently set up a blog where you will find regular updates on our progress and some technical devblog articles that might be interesting to you: http://upvoid.com
We are working on this for some time now, so we are grateful for any feedback. Let us hear what you think!