This script in intended to help modelers keep their geometry clean during or after the modeling process.
It is not the end-all cleaning script, it only operates on polygons, nurbs, curves, subdivs and group nodes. In other words your Maya scene may still need to be cleaned before being handed off in production (DAG objects and whatnot).

Here is what the script checks for and fixes if possible.

Polygons:
- Deletes History
- Merges vertices within .0001 of each other
- Center's object pivot point
- Unlocks any locked channels
- Deletes any incoming information in to channels (such as animation)
- Confoms all face normals
- Sets all face normals to face
- Sets all edge normals to hard
- Unlocks all vertex normals
- Assigns default shader
- Freezes Transformations
- Deletes History again

NURBS, CURVES, SUBDIVS AND GROUPS (transform nodes):
- Deletes History
- Center's object pivot point
- Unlocks any locked channels
- Deletes any incoming information in to channels (such as animation)
- Freezes Transformations
- Deletes History again

To Install and use:
Copy script in to your script directory. (i.e. My Documents/maya/7.0/scripts/)

In script editor or command line, type the following (or add these lines to a hotkey / shelf button)

source EJL_modelClean.mel;
EJL_modelClean;

Be careful with this script on unusually dense models such as scan data. Depending on your computer you may experience a system lockup!