DEVONthink - DEVONtechnologies develops DEVONthink, DEVONagent, and other Mac and iOS apps for document and information management and web research.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
HoudahSpot - Advanced File Search Utility for Mac OS X
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.
EndNote - Accelerate Your Research. Save time, stay organized, collaborate with colleagues and get published with EndNote 20.