Tags are keywords meant to facilitate classification for web pages, photos, blogs, bookmarks, and anything elese that exists on the web. Social bookmarking allows users to set up a list of bookmarks on the web. By adding tags to bookmarks and aggregating bookmarks across users, people can search for the top web pages on a given topic.
RSS is standard for sending frequently updated web content to users. The advantage of RSS feed readers is that updates to your subscribed "channels" are delivered automatically to your RSS news reader in an easy to browse format.
Allows ranking of items (photos, news articles) by many users, highlighting those items that users find interesting or useful The most familiar use of this capability is by Amazon.com.
Users can enter keywords and receive emailed news articles containing those keywords.
A website that stores documents and provides a directory and searching capabilities can be used as a virtual library or resource center on the web.
One stop customized web pages that allow users to pick the content that is displayed by choosing modules. (e.g. viewing email, calendar, news feeds and sports scores all on one page)