So I just started working on this procedurally generated voxel/boxel terrain thing for my computer graphics final project. The above screen shot is what it looks like after a couple hours of work. That's a 200x200 grid. And yes, sadly, that is 19 frames per second.
Right now, I'm just generating the terrain using 2D Perlin noise stored in a heightmap. Using a heightmap isn't really ideal since I can't really use it to store caves or overhangs. Eventually I'm going to update that to an octtree and use some combination of 3D Perlin noise stuff for generating the map.
For drawing, I just draw every single block which pretty much explains the 19 FPS. I have some ideas for optimizing it, such as only drawing blocks that are inside the view frustum and only drawing faces that are touching empty blocks, but I haven't gotten around to doing that. My OpenGL skills aren't there yet.
I'll post some more when I have more to show.