DEVONthink - DEVONtechnologies develops DEVONthink, DEVONagent, and other Mac and iOS apps for document and information management and web research.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
TaskSurfer - TaskSurfer gives you all of the tools you need to manage things the way you want.
HoudahSpot - Advanced File Search Utility for Mac OS X
IDocument - Feel powerless of your documents chaos in your Mac?
Keep It - Write notes, keep things, and find them again