Implementing tag clouds and publish/subscribe feeds

http://scalablecorner.blogspot.com/2007/06/implementing-tag-cloud-nasty-way-part-2.html

http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging

http://www.royans.net/arch/mongodb/

http://rochakchauhan.com/blog/2008/09/15/how-to-implement-tag-clouds-in-php/

http://wijix.com/post/Simple-Tag-Cloud-Implementation-for-ASPNET-MVC.aspx

http://stackoverflow.com/questions/4740730/what-is-the-best-scalable-fast-reliable-approach-to-implement-an-activity-fe

http://highscalability.com/blog/2007/11/6/quick-question-about-efficiently-implementing-facebook-news.html

http://stackoverflow.com/questions/1443960/how-to-implement-the-activity-stream-in-a-social-network

http://blog.gigya.com/implementing-simple-activity-feeds-developers-pad/