With all the information that is consumed electronically, several established 'cloud computing' sites (sites that store information on the "cloud") have been created to collect what we discover online and store it for us.
Some of these have moved beyond simple 'bookmarking' to create share communities, including mechanisms for instructors and students to share and communicate in a 'group' setting. Some offer downloads to enable content to be viewed offline.
Share & commenting features are what differentiate these sites from simple feed readers and aggregators, although lines continue to blur with all of these tools.
Here are a few of the more common sites:
Source: Diigo