These sites are:
Info about delicious:
del.icio.us is a collection of favorites - yours and everyone else's. Use del.icio.us to:
* Keep links to your favorite articles, blogs, music, restaurant reviews, and more on del.icio.us and access them from any computer on the web.
* Share favorites with friends, family, and colleagues.
* Discover new things. Everything on del.icio.us is someone's favorite - they've already done the work of finding it. Explore and enjoy.
A source for what's new and popular on the web -- personalized for you. We want to democratize the traditional model by giving editorial control to the people who use the site, not those who run it. Your votes train a filter, so let reddit know what you liked and disliked, because you'll begin to be recommended links filtered to your tastes. All of the content on reddit is from users who are rewarded for good submissions (and punished for bad ones) by their peers; you decide what appears on your front page and which submissions rise to fame or fall into obscurity.
Digg is a user driven social content website. Ok, so what the heck does that mean? Well, everything on digg is submitted by the digg user community (that would be you). After you submit content, other digg users read your submission and digg what they like best. If your story rocks and receives enough diggs, it is promoted to the front page for the millions of digg visitors to see.