This document compares the social bookmarking sites Delicious and Diigo. It begins by explaining what social bookmarking is and how it allows users to save web pages and organize them using tags. It then discusses the key features of each site, such as how bookmarks can be shared publicly on Delicious, while Diigo offers additional tools like bookmark highlighting and notetaking. Finally, the document notes that while Delicious was one of the earliest social bookmarking sites, Diigo has more recently evolved to provide more collaborative features for organizing bookmarks in groups and classes.