This is a .NET re-write of a tool I wrote many years ago in VB6 and placed on ArcScripts.
http://arcscripts.esri.com/details.asp?dbid=14236
It allows you to quickly filter the current contents view in ArcCatalog. The filter is based simply on a string 'contains' function. Regex support could be added at some point but not everyone is comfortable with the syntax. After adding the AddIn, you should have a new toolbar called 'Quick Find'. The toolbar has a combobox that you can type into and a clear button. If you hit 'Enter' the filter text should get added to the combo box list entries so you can go re-use it or see what filters you've used.
Currently it is built for ArcGIS Desktop 10.1 with Visual Studio 2010 Pro.
Also this a work in progress so let me know if things are not working. There might be some refinement needed in the dropdown list entry management.