DEVONthink - DEVONtechnologies develops DEVONthink, DEVONagent, and other Mac and iOS apps for document and information management and web research.
TagFlow - TagFlow is an intelligent files manager that use tags for organize your documents.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
TaggedFrog - Based on the convenient drag ’n’ drop technique, TaggedFrog allows you to organize your files...
HoudahSpot - Advanced File Search Utility for Mac OS X
One Commander - Your next file manager