NiftyBox!

Based on the convenient drag ’n’ drop technique, TaggedFrog allows you to organize your files, documents and Web links. Just add objects to the library and tag them with any keywords. That’s it. You can forget the file name or where the file is located, but dont worry - the tags will find the file for you. You can tag Web links, Microsoft Office documents, PDF documents and images. In fact, you can tag any kind of file. And if you wish, you can tag each and every file on your hard drive!

TagLists is a small application for OS X that allows you to quickly see which files you've tagged with particular tags. It uses the OpenMeta tagging system, which means that it finds files that have been tagged with any of the applications that support OpenMeta.

File tagging and rating utility for OS X.

TagoMan frees you from constrains of your folders.