This is a fairly optimized implementation of a CLOD terrain renderer I've written in Spring 2002. Unfortunately I've forgotten which paper I used for this implementation (IIRC it was the same algorithm as Aquanox(TM)?).It is written in plain ISO C. Its main goals are minimal dependencies and easy handling. The static lib is sized only 30K. You can adjust the quality of rendering on the fly by adjusting a simple floating point parameter. So far, it supports only square sized terrains.
It is hosted on sourceforge
You can get MTR on the sourceforge project pages.