The Elder Scrolls III: Morrowind [official site] was released in 2002. It's testament to how highly regarded the now 13-year-old game is that folks are still determined to keep it alive. OpenMW is one such effort: an open source "engine re-implementation" of Morrowind. It's still some ways from being finished, but the released build has just received an extensive update.
Version 0.37.0 sees OpenMW's graphics engine rewritten by introducing the high performance 3D graphics toolkit OpenSceneGraph. The new renderer will not only boost the engine aesthetically, but will also increase performance speedup. In the interest of getting it out without further delay, certain features have been temporarily compromised as a result of the update, but the OpenMW team assure these will be re-added "soon". The update's comprehensive changelog can be found here, however here's the blurb speaking to this point as it appears on the site:
You may notice that shadows are not re-implemented at this time, as well as distant land and object shaders, but we wanted to get the release out rather than delay any further! These features will be re-added soon! This release brings many other changes and bugfixes, as well as a huge amount of new work done on OpenCS, the editor for OpenMW. Some features are missing from OpenCS as well: only basic camera controls are implemented, pathgrid and cell marker rendering is missing, as well as instance moving.
As Graham previously pointed out, other Morrowind overhauls you might've heard of before include: Skywind, which takes Morrowind to Skyrim; Morroblivion, which attempts the same only to Oblivion; and Morrowind Overhaul 3, a cosmetic graphical mod. OpenMW differs from those in that it's a standalone engine, designed not simply with a graphical upgrade in mind but intended to futureproof the game for modern CPUs and to build a toolkit that can even be used to make new mods or games.
If you're keen to find out more about the nuts and bolts, whys and hows of OpenMW, the creators offer this Q&A: