Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Bloomerang - Bloomerang is a simple donor database and fundraising software solution that helps nonprofits decrease donor attrition and increase revenue.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.
Kindful - Nonprofit donor database + fundraising tools all in one
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
Classy - Expressive, flexible, and powerful stylesheets for native iOS apps