This is an intresting tool I used a lot to split a layer by attribute .
The tool takes a single shapefile and splits it into many shapefiles based on the unique values of a chosen field
1. Open ArcMap
2. Open Arctoolbox.
3. Right click on the top level of the Toolbox and you should see a menu come up and one of the choices will be add toolbox.
4. Navigate to the python directory and add the .tbx file.
Download :
http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=37AEB018-1422-2418-A036-CA6D9920F808
