Digital Projects Toolkit

Web - free.
Diigo is a social bookmarking webiste that lets you save pages, tag them, annotate them, and share them with others.

Web; Mac/Windows/Linux; iOS/Android - free.
Evernote allows you to take notes and save resources across devices. Groups can use shared notebooks to work collaboratively.

Web - free. Hypothes.is allows you to annotate anything you see on the web (or via a browser, like PDFs) and save your notes. You may share your notes with specific groups or publicly.

Windows/Mac/Linux - free.
Zotero collects and manages citation information from your research, allowing you to generate bibliographies, share resources, and even create in-text citations as you write, with an additional Word or OpenOffice/LibreOffice plugin.