Now this is another cool use of MacFUSE. SpotlightFS is a filesystem that creates smart folders. You can create a folder with the name of a Spotlight query, and all of the matching files will appear in the folder. Also, you can use the SmarterFolder to create arbitrary results.
The main difference about SpotlightFS and the Finder's Smart folders, is that the Finder's Smart Folders aren't directories. With SpotlightFS, you can look in these directories through the command line.
[via Unixjunkie Blog]