Carrot2 is an open source search results clustering engine. It automatically organizes small collections of documents into categories.

Delicious is a social bookmarking service that allows users to tag, save, manage, and share web pages from a centralized source.

Eventseer is a personalized tracker that alerts you when a new event matches your interests (people, topics, organizations). You may contribute material on your personal research whiteboard, such as job offers, requests for reviewers, or information about software releases.

Google Notebook helps you collect notes and information from the web for research or planning. You can use Google's bookmarklet to add text and images to any page of your notebooks, access your notebooks from any computer or your mobile phone, and also share your notebooks with others.

Google announced they are no longer actively developing Google Notebook, but are continuing to maintain the service.

NoteBook is an application that offers a notebook-like interface for organizing digital information. Technical features include the ability to take notes and edit, add sticky notes, copy/paste information, diagram and sketch, annotate, import/export files, and more.

View and edit files from different cloud services (e.g. Dropbox, Google Drive, etc.) in one place.

Pliny is a note-taking and annotation tool. It may be used with both digital (web pages, images, PDF files) and non-digital (books, printed articles) materials. Pliny is a desktop application that runs on your computer, and manages annotations and notes that you gather as you are reading.

Springpad allows you to create, organize and share annotations and notes. You may bookmark web pages, search online products, use tags to better organize your information, create your own digital cork-board, and share your information by making your pages "public."

SuperMemo is a learning software that is devoted to increasing the speed of learning and heightening the level of knowledge retention.