I am putting the finishing touches on my latest asset MeshBaker LOD. This asset combines level of detail meshes into clusters and bakes the clusters into combined meshes. As the camera moves closer and further away from the objects the LODs are updated in the combined mesh. It can also be used with skinned meshes to create mobs.
The initial testing for this is fantastic. It is bringing me one step closer to my dream of easily creating huge sandbox worlds. I will be posting more information soon.