RhinoResurf gives Rhino the ability to reconstruct the geometry.
Edit By BS Editor: RhinoResurf for Rhino is a reverse engineering plug-in for Rhinoceros 3.0 and 4.0. This plug-in gives Rhino the ability to reconstruct the geometry represented by NURB surface of an object from a mesh or point Cloud which describes it.

RhinoResurf for Rhino can drape a surface over a point cloud with specified tolerance. Draping a surface is similar to laying a piece of cloth over an object. The surface is deformed to take the shape of the object along the drape direction. The drape direction is calculated automatically. Command: RsPoints2Surf

RhinoResurf for Rhino can convert an open mesh model to a single NURB surface with specified tolerance. The mesh is allowed to have interior holes in the model. Command: RsMesh2Surf

RhinoResurf for Rhino can convert sub-mesh in an open mesh to a single NURB surface with specified tolerance. User selects a mesh, and defines a sub-mesh by drawing closed lines on the selected mesh. Then just click right-mouse button, the sub-mesh will be converted to a NURB surface. Command: RsMesh2Surf

RhinoResurf for Rhino can convert an open or closed mesh to multiple NURB surfaces. User selects a mesh, and defines a curve network by drawing lines on the selected mesh. Then just click one or two buttons, the selected mesh will be converted to multiple NURB surfaces with specified tolerance. The transition Between any two NURBS surface patches reaches G1 Continuity. Command: RsMesh2Surfs

RhinoResurf for Rhino can merge several meshes into one mesh body. Command: RsMergeMeshs

Features of RhinoResurf:

NURBS fitting with specified tolerance.

Controllable surface smoothness.

G1 continuity transition.

Powerful ability to fit large scale point cloud/mesh to a single face.

Fully automated nurbs surfaces generation.
you can free download RhinoResurf for Rhino4 1.1.56 now.