Social Bookmarking Tools:

• - Social Bookmarking. Keep your bookmarks online so they are with you at any computer. 
• - Social Bookmarking tool that lets you annotate the sites you bookmark.
• - SimplyBox lets you bookmark and save snippets of websites and organize them in "boxes" that can be shared with other users.
• - Annotate websites and share your annotations with other A.nnotate users.

Related tools:

• - Search your del.icio.us bookmarks with Google algorithms. Can be used to create your own custom search engine.
• - Search engine that only returns items that have been bookmarked or voted for by people on social bookmarking sites.
• - Place post-it notes on any web page and share them on Twitter
•   - Create a post-it note on a a webpage, upload a file to that post-it to share with others, then share the post-it on Twitter.
• - Displays the 50 most tweeted links and shows you what people are saying about them.

Resources:

• Using del.icio.us In Education
• 7 Things You Should Know About Social Bookmarking
• Wikipedia: Social Bookmarking
• FOLKSONOMIES AND TAGGING:
• Top 5 social bookmarking services