Social bookmarking sites allow users to save, organize, and share web pages. Popular social bookmarking sites include Digg, Reddit, StumbleUpon, and Delicious. Digg focuses on trending news and viral content. Reddit allows users to discover trending topics and share memes and videos. StumbleUpon uses peer recommendations to discover personalized web pages, photos and videos. Delicious allows users to store bookmarks online with tags for flexible organization.