Mendeley is a "free reference manager and academic social network". It aims to work as a central hub for your research material. Known for its wide variety of features such as PDF highlighting/note taking and automatic extracting of metadata from PDF files.

• Mendeley Desktop: a Qt based reference and PDF manager for Linux, Mac and Windows
• Mendeley Web: Online social media platform
• Free account includes 2GB storage (upgradable to a premium account)
• All data stored in the cloud, cannot be used without an account
• Citation/bibliography plugin for LibreOffice/MS Office
• Mobile versions also available (Android/IOS)
• Database can be linked with Zotero
• Works with BibTeX

Resources

• Mendeley Help Guides
• Mendeley Support
• Mendeley LibGuide
• Download and Edit Citation Styles
• Twitter: Mendeley

Zotero is a "free, easy-to-use tool to help you collect, organize, cite and share your resource sources". Originally a Firefox extension, now also available as a standalone desktop program. Enables you to easily scrape bibliographic metadata from web pages.

• Zotero for Firefox: runs embedded in the browser (click the "Z" button in the toolbar to open)
• Zotero Standalone: browser-independent desktop application. In order to access browser-based features such metadata scraping you will also need to install a browser extension.
• Free account needed to sync your library online (but can be used without an account)
• Citation/bibliography plugin for LibreOffice/MS Office
• Database can be linked with Mendeley
• Functionality can be extended via plugins
• Works with BibTeX and additional functionality available via third party plugins

Resources

• Zotero Quick Start Guide
• Zotero Documentation
• How to Edit Citation Styles
• Download Citation Styles
• Twitter: Zotero

This page is covers reference managers that are usually used with "what you see is what you get" type text processors such as OpenOffice and MS Word.

LaTeX on the other hand is an in depth document preparation system mostly used for complex scientific writing. LaTeX has its own page in the top menu.