Del.icio.us

From Bloggerhacks

Del.icio.us is a social bookmarking site; social bookmarking refers to the process of creating bookmarks—just like in a traditional web browser—but storing and categorizing them in an online repository and sharing them with others. Users who partake in social bookmarking offer their lists for subscription, and subscribe to the lists of others.

De.icio.us is often used as a third-party resource for adding functionality to your Blogger blog.