Diigo and Delicious are free online social bookmarking services that allow users to collect and archive links to websites that can be accessed in the future and shared with others. Delicious and Diigo allow users to organize their web links using keyword tags that can be searched and shared between users. Diigo also has annotation features in addition to adding keyword tags where users can highlight, share comments on sticky notes, organize links into user generated lists, and share links with groups of other users. Diigo will also post bookmarked links to a user's Delicious account to broaden connections and sharing between users. Diigo and Delicious are great tools for students and teachers to share links to web sites for collaboration and sharing new knowledge. 

Diigo has an educator version where teachers can create and manage accounts for their students, making it easy to get all students using Diigo and putting the power of Diigo to use for student learning.