I wasn’t going to post this here because I made it, but I was asked to as soon as I open sourced it. It can generate terrain with oceans, mountains, islands, etc
Right now, it has a few set values, but you can manipulate them as much as you want.
Open sourced, and the Diamond-Square algo is almost completely ROBLOX indendant; remove those waits to get it to be completely free.
Looks neat! 
I’m still trying to understand how it works.
I recommend using this and this as reference, they really helped me. You might also want to take a look at my visual midpoint displacement, which is like a 1D form of Diamond-Square (well, technically, diamond-square is an ‘improved’ midpoint displacement for 2d).
The Diamond-Square algorithm makes really nice terrain and is used by Terragen.
I made one as well a few months ago.
http://www.roblox.com/Project-Diamond-Square-Terrain-Generator-place?id=4039966
The terrain it produces is pretty neat. It seems common for me to get a primarily green, boring, terrain 
I also learned that you cannot upvote a game if you open it only with edit
I made an infinite one a while back
Infinite Random Terrain
If you wanted to triangle terrain it, Section2B’s BuildIn Libraries is a fast and efficient triangle drawer, that can also draw quads, etc, and many advantages over a plain triangle script 
I need to figure out how to visualise this using parts, or Guis, or something.
Obviously the 1D one first, of course. The 2D one would be next.
I guess 3D would be for animated 2D clouds.