I suspect this isn’t new to most ESRI users out there, but the ESRI Developer Network hosts a large number of free, useful, downloadable utilities for most of ESRI’s current and former products at the Code Exchange (click on “Search ArcScripts” and select your desired product for the useful stuff). For example, here’s a direct link to a listing of 1130 utility scripts for ArcGIS Desktop.
Thanks to Valery Hronusov for the tip.