Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
HoudahSpot - Advanced File Search Utility for Mac OS X
Tabbles - Tabbles use tags to organize and find files along with your colleagues.
Elyse - The free version allows up to 30 tags.
allTags - allTags is a free, tag based file management application.
Yojimbo - Yojimbo makes keeping all the small (or even large) bits of information that pour in every day...