Dockable Explorer Plugin for Notepad++ 4.0 and higher. Features:
Tree, file list, Favorites, filtering, sorting and many more...
Have a look here for main prog:
Try out and have fun
This plugin is not working on N++ 6.5 :( It was good while it worked.
This is really good for searching for files by content. It has some advanced search features and the reporting comes in a tree format with some lines highlighted. It is easy to read.