In Mac OS X’s Finder, you can save searches as “Smart Folders”. These give you quick access to all your files that meet certain criteria. For example, all Microsoft Word files modified this month. All JPG photos taken with a specific camera. Or all e-mails you’ve received from certain senders within the last seven days.
Because Mac OS X Smart Folders are actually saved searches, they differ from regular folders: they don’t actually hold anything – they only list files stored elsewhere. The content of Smart Folder is not static but dynamic. It is updated continuously as new files come to meet the smart folder’s search criteria. This means that its content changes every time files on your Mac are added, changed, or removed.
With HoudahSpot (4.1 or later), you can easily set up a search and export it as a Finder Smart Folder.