allTags was developed to manage large file sets efficiently. Time-consuming actions, like naming files and choosing folders, are replaced by fast tagging operations.
With built-in support functions, allTags avoids inconsistencies and speeds up file description and retrieval. allTags is 100% free to use.
TagSpaces - TagSpaces is an open source platform for personal data management. With TagSpaces you can manage and organize the files on your laptop, tablet or smart phone.
HoudahSpot - Advanced File Search Utility for Mac OS X
TMSU - TMSU is a tool for tagging your files.
Yojimbo - Yojimbo makes keeping all the small (or even large) bits of information that pour in every day...
Tabbles - Tabbles use tags to organize and find files along with your colleagues.
DEVONthink - DEVONtechnologies develops DEVONthink, DEVONagent, and other Mac and iOS apps for document and information management and web research.