Diigo is two services in one: it is a research and collaborative research tool on the one hand, and a knowledge-sharing community and social content site on the other. Research: Instead of just bookmarking, Diigo allows to highlight text and attach sticky notes to specific parts of web pages. Diigo highlights and sticky notes are persistent in the sense that whenever the user returns to the original web page, they are still evident. Archive: users can search their collections not only by tags, but also by full-text, including highlights, sticky notes, titles, etc of the web pages. Organize: tags and lists are two different ways to organize information. Search and access from anywhere, anytime: users can easily switch between several search modes in "My Library", by tags, full-text or advanced search. Since all data are stored in user’s Diigo account on the web, users can access them from any computer with internet access. Share: users can keep things private or public, or shared with a group. Publish their findings on blogs by using "Send to Blog" feature, by setting up automatic daily posting, or by adding linkrolls and tagrolls to blogs. Users can also easily post to other sites like twitter, facebook, delicious, etc. Build a Personal Learning Network: since bookmarks, tags, and annotations are a great expression of a person's interests and expertise, users can search for people by name or user name, import friends, invite friends via emails, and make friend lists to build their Personal Learning Network. Create a private or public group for company, class, and team: A Diigo group can be public, private or semi-private. When a member of a Diigo group comes across a web page, he can highlight, tag, and share it to the group. In this way, group bookmarks become a repository of collective research. Various sorting methods (by most recent vs. popularity) make it easy to spot relevant resources. Diigo Educator Account These are special premium accounts provided specifically to K-12 & higher education educators. • Teacher can create student accounts for an entire class with just a few clicks (and student email addresses are optional for account creation) • Students of the same class are automatically set up as a Diigo group so they can start using all the benefits that a Diigo group provides, such as group bookmarks and annotations, and group forums. • Privacy settings of student accounts are pre-set so that only teachers and classmates can communicate with them. • Ads presented to student account users are limited to education-related sponsors.
Resources required: 
PC and Mac, any browsers, Android, iPhone, iPad.
Free: unlimited bookmarks, 1000/year highlights, 30 total cached pages. Education Basic Plan (free): unlimited bookmarks, 20 Cached pages/month , unlimited Highlights and Teacher Console. Basic plan (20 USD/year): unlimited bookmarks, unlimited highlights, full text search, ads free. Premium plan (5 USD/month, 40 USD/year): basic plan + unlimited cached pages, unlimited screen captures, priority support.
Setup and configuration: 
To enjoy the full benefits of Diigo (seamless bookmarking, tagging, highlighting, clipping, sharing, annotating, searching, etc), the Diigo toolbar (ie. a browser add-on extension) can be installed. This is available in the following browsers: Firefox 2.
Only certain viewing and filtering options are allowed.
Navigation and operation: 
Simple and intuitive tool
How to use it: 
Useful video guide for new users: http://www.diigo.com/learn_more More information: http://help.diigo.com/how-to-guide
Examples of use: 
As users read on the web, instead of just bookmarking, they can highlight portions of web pages that are of particular interest to them. Users can also attach sticky notes to specific parts of web pages, also tags and description. All marks are collected in My library and can be easily found by file types, tags or lists.
Useful tips: 
There are many useful tools for different browsers, Android, iPad and iPhone. Learn more: http://www.diigo.com/tools