As we are discovering, there are often things we want to do but ArcGIS is not able to do them.  Esri has created a Tool Gallery for people to share tools they have created when ArcGIS cannot do what they want.   If you are thinking about creating a tool to do something you need, it is worth checking here first so that you don’t have to re-create the wheel.

http://resources.arcgis.com/en/communities/analysis/

http://resources.arcgis.com/gallery/file/geoprocessing