Google Chrome app: https://chrome.google.com/webstore/detail/diigo-bookmark-archive-hi/oojbgadfejifecebmdnhhkbhdjaphole
Mozilla Firefox extension: https://addons.mozilla.org/en-US/firefox/addon/diigo-web-highlighter-and-stic/
Free iPad app: https://itunes.apple.com/us/app/diigo/id417202559?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/diigo-offline-reader/id335006600?mt=8&uo=4&at=10l6SU
Website: http://www.diigo.com/
Website: http://sqworl.com/
Website: http://www.symbaloo.com/
Free Android Phone app: https://play.google.com/store/apps/details?id=com.symbaloo.android
Free iPhone app: https://itunes.apple.com/us/app/symbaloo-bookmark-share-your/id521081559?mt=8&uo=4&at=10l6SU
Google Chrome app: https://chrome.google.com/webstore/detail/symbaloo/dfnbdccaiknlpdgabdgjijniolkgmoeh
Free Android Phone app: https://play.google.com/store/apps/details?id=com.zite
Free iPad app: http://itunes.apple.com/us/app/zite/id419752338?mt=8&ls=1&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/us/app/zite/id419752338?mt=8&ls=1&uo=4&at=10l6SU
Website: http://delicious.com/
Free Android Phone app: https://play.google.com/store/apps/details?id=com.ideashower.readitlater.pro
Google Chrome app: https://chrome.google.com/webstore/detail/pocket-formerly-read-it-l/niloccemoadcdkdjlinkgdfekeahmflj
Mozilla Firefox extension: https://addons.mozilla.org/en-US/firefox/addon/read-it-later/
Free iPad app: http://itunes.apple.com/us/app/pocket-formerly-read-it-later/id309601447?mt=8&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/us/app/pocket-formerly-read-it-later/id309601447?mt=8&uo=4&at=10l6SU
Apple Safari extension: http://getpocket.com/safari/
Website: http://getpocket.com/
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.ideashower.readitlater.pro
Website: http://edu.symbaloo.com/
Free Android Phone app: https://play.google.com/store/apps/details?id=com.symbaloo.edu.android
Free iPhone app: https://itunes.apple.com/us/app/symbalooedu-organize-share/id536165032?mt=8&uo=4&at=10l6SU
Website: http://www.stumbleupon.com/
Free iPad app: https://itunes.apple.com/us/app/stumbleupon!/id386244833?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/stumbleupon!/id386244833?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.stumbleupon.android.app
Google Chrome app: https://chrome.google.com/webstore/detail/stumbleupon/kcahibnffhnnjcedflmchmokndkjnhpg
Mozilla Firefox extension: https://addons.mozilla.org/en-US/firefox/addon/stumbleupon/