Here are some of the best social bookmarking websites I would recommend to teachers and students.
1- Diigo
Diigo helps you save and organize online content for easy access anytime, anywhere. It also allows you to annotate web pages and PDFs and, using Outliner, you will be able to create structured research hub from links and curated content. You can also insert text and sticky notes directly on any web page. Diigo collaborative features enable you to share your bookmarks with groups and colleagues.
2- Livebinder
3- Scoop.it
Scoop.it is another good social bookmarking tool for curating digital content. Similar to Pinterest, Scoop.it allows you to create as many boards as you want and you can either share them with the public or make them private. It also has a handy bookmarklet to use for instant Scooping.4- Pinterest
Pinterest is a free web tool that you can use to visually curate web content. You can create as many boards as you want and you can also join other's boards and start a collaborative pinning experience. Pinterest has a handy bookmarklet that you can drag to the bookmarks toolbar and with one click you will be able to add anything you come across.5- Symbaloo
Symbaloo is a personal startpage that allows you to easily navigate the web and compile your favorite sites all in to one visual interface. Save your bookmarks in the cloud and access them from anywhere with any device.
6. Flipboard
Flipboard is another excellent bookmarking tool to help you curate the web for educational materials and resources to use in your teaching. Flipboard lets you save web content such as videos, images, articles, etc into magazine style boards. You can design magazines on any topic you want and start adding content to it.You can also share your magazines with other teachers, students, parents, and so forth. Flipboard is available as a Chrome extension, a browser button, and a mobile app for iOS and Android. Like Instapaper, you need to register your account with Flipboard to start saving and curating web content.
7. Pocket
Pocket is a bookmarking tool that lets you instantly save web content to your personal Pocket library to read at your pace and at the time most convenient to you. Besides bookmarking content, Pocket also provides you with the tools to enhance your reading experience including tools to tailor text sizes, change font styles, adjust viewing modes, remove clutter, organize saves using tags, keep track of key passages using highlights, and more. Pocket also offers text to speech service allowing you to listen to your articles on the go using mobile app.