Search saved using Apple's Spotlight program, included with Mac OS X 10.4 and later; saved as a "Smart Folder," which dynamically updates based on the search parameters saved with the folder.

Spotlight searches can be saved by performing a Spotlight search and selecting "Show All" in the Spotlight menu, then clicking "Save" in the results window that appears in the Finder. The default location for saved searches is "~user/Library/Saved Searches."